A crosslinking material and uses thereof

ABSTRACT

A crosslinking material, the crosslinking material comprising the reaction product of a reaction mixture comprising: (ii) ≥70% by weight of a cyclic unsaturated acid anhydride and/or diacid derivative thereof by total solid weight of the monomers from which the crosslinking material is formed; (ii) optionally, an ethylenically unsaturated monomer; and (iii) optionally, an alcohol, amine, thiol and/or water, wherein at least a portion of the cyclic unsaturated acid anhydride and/or diacid derivative thereof is reacted with the alcohol, amine, thiol and/or water, when present; and wherein the crosslinking material has an acid number of at least 100 mg KOH/g.

FIELD OF THE INVENTION

The present invention relates to a crosslinking material, in particularto a crosslinking material comprising the reaction product of a reactionmixture comprising ≥70% by weight of a cyclic unsaturated acid anhydrideand/or diacid derivative thereof by total solid weight of the monomersfrom which the crosslinking material is formed. The present inventionextends to a coating composition comprising a film-forming resin andsaid crosslinking material and to a package coated on at least a portionthereof with a coating, the coating being derived from a coatingcomposition comprising a film-forming resin and said crosslinkingmaterial.

BACKGROUND OF THE INVENTION

Coatings are applied to numerous substrates to provide protective and/ordecorative qualities. These coatings are often thermoset coatings, whichcure upon reaction of a functional resin with a crosslinking materialhaving functionality that reacts with the functionality of the resin.Crosslinkers are often formaldehyde based. Many industries areinterested in reducing if not eliminating formaldehyde in coatings.Coatings that are substantially, essentially or completely free offormaldehyde are desired.

SUMMARY OF THE INVENTION

According to the present invention there is provided a crosslinkingmaterial, the crosslinking material comprising the reaction product of areaction mixture comprising:

-   -   (i) ≥70% by weight of a cyclic unsaturated acid anhydride and/or        diacid derivative thereof by total solid weight of the monomers        from which the crosslinking material is formed;    -   (ii) optionally, an ethylenically unsaturated monomer; and    -   (iii) optionally, an alcohol, amine, thiol and/or water, wherein        at least a portion of the cyclic unsaturated acid anhydride        and/or diacid derivative thereof is reacted with the alcohol,        amine, thiol and/or water; when present and wherein the        crosslinking material has an acid number of at least 100 mg        KOH/g.

There is also provided a coating composition, the coating compositioncomprising:

-   -   (a) a film-forming resin having a functional group having an        active hydrogen atom; and    -   (b) a crosslinking material operable to crosslink the functional        group having an active hydrogen atom on the film-forming resin,        the crosslinking material comprising the reaction product of a        reaction mixture comprising:        -   (i) ≥70% by weight of a cyclic unsaturated acid anhydride            and/or diacid derivative thereof by total solid weight of            the monomers from which the crosslinking material is formed;        -   (ii) optionally, an ethylenically unsaturated monomer; and        -   (iii) optionally, an alcohol, amine, thiol and/or water,            wherein at least a portion of the cyclic unsaturated acid            anhydride and/or diacid derivative thereof is reacted with            the alcohol, amine, thiol and/or water, when present;            and wherein the crosslinking material has an acid number of            at least 100 mg KOH/g.

There is also provided a substrate coated on at least a portion thereofwith a coating, the coating being derived from a coating composition,the coating composition comprising:

-   -   (a) a film-forming resin having a functional group having an        active hydrogen atom; and    -   (b) a crosslinking material operable to crosslink the functional        group having an active hydrogen atom on the film-forming resin,        the crosslinking material comprising the reaction product of a        reaction mixture comprising:        -   (i) ≥70% by weight of a cyclic unsaturated acid anhydride            and/or diacid derivative thereof by total solid weight of            the monomers from which the crosslinking material is formed;        -   (ii) optionally, an ethylenically unsaturated monomer; and        -   (iii) optionally, an alcohol, amine, thiol and/or water,            wherein at least a portion of the cyclic unsaturated acid            anhydride and/or diacid derivative thereof is reacted with            the alcohol, amine, thiol and/or water, when present;            and wherein the crosslinking material has an acid number of            at least 100 mg KOH/g.

There is also provided a package coated on at least a portion thereofwith a coating, the coating being derived from a coating composition,the coating composition comprising:

-   -   (a) a film-forming resin having a functional group having an        active hydrogen atom; and    -   (b) a crosslinking material operable to crosslink the functional        group having an active hydrogen atom on the film-forming resin,        the crosslinking material comprising the reaction product of a        reaction mixture comprising:        -   (i) ≥70% by weight of a cyclic unsaturated acid anhydride            and/or diacid derivative thereof by total solid weight of            the monomers from which the crosslinking material is formed;        -   (ii) optionally, an ethylenically unsaturated monomer; and        -   (iii) optionally, an alcohol, amine, thiol and/or water,            wherein at least a portion of the cyclic unsaturated acid            anhydride and/or diacid derivative thereof is reacted with            the alcohol, amine, thiol and/or water, when present;            and wherein the crosslinking material has an acid number of            at least 100 mg KOH/g.

There is also provided the use of a material as a crosslinker forcrosslinking a film-forming resin, the material comprising the reactionproduct of a reaction mixture comprising:

-   -   (ii) ≥70% by weight of a cyclic unsaturated acid anhydride        and/or diacid derivative thereof by total solid weight of the        monomers from which the crosslinking material is formed;    -   (ii) optionally, an ethylenically unsaturated monomer; and    -   (iii) optionally, an alcohol, amine, thiol and/or water, wherein        at least a portion of the cyclic unsaturated acid anhydride        and/or diacid derivative thereof is reacted with the alcohol,        amine, thiol and/or water, when present;        and wherein the crosslinking material has an acid number of at        least 100 mg KOH/g.

There is also provided a method of crosslinking a film-forming resin,comprising using a crosslinking material to crosslink the film-formingresin, the crosslinking material comprising the reaction product of areaction mixture comprising:

-   -   (iii) ≥70% by weight of a cyclic unsaturated acid anhydride        and/or diacid derivative thereof by total solid weight of the        monomers from which the crosslinking material is formed;    -   (ii) optionally, an ethylenically unsaturated monomer; and    -   (iii) optionally, an alcohol, amine, thiol and/or water, wherein        at least a portion of the cyclic unsaturated acid anhydride        and/or diacid derivative thereof is reacted with the alcohol,        amine, thiol and/or water, when present;        and wherein the crosslinking material has an acid number of at        least 100 mg KOH/g.

DETAILED DESCRIPTION OF THE INVENTION

The crosslinking material comprises the reaction product of a reactionmixture comprising (i) a cyclic unsaturated acid anhydride and/or diacidderivative thereof.

The cyclic unsaturated acid anhydride may be any suitable cyclicunsaturated acid anhydride. The cyclic unsaturated acid anhydride may beany suitable cyclic unsaturated acid anhydride that is able to undergopolymerisation, for example, free radical polymerisation, optionallywith an ethylenically unsaturated monomer. Suitable cyclic unsaturatedacid anhydrides will be known to a person skilled in the art. Examplesof suitable cyclic unsaturated acid anhydrides include, but are notlimited to, maleic anhydride, tetrahydrophthalic anhydride,methyltetrahydrophthalic anhydride, vinylhexahydrophthalic anhydride,chlorendic anhydride, methyl-endomethylenetetrahydrophthalic anhydride,itaconic anhydride, citraconic anhydride, alkenyl succinic anhydridessuch as, for example, allyl succinic anhydride and dodecenyl succinicanhydride, norbornene anhydride and combinations thereof.

The cyclic unsaturated acid anhydride may be maleic anhydride.

‘Diacid derivative’ of the cyclic unsaturated acid anhydride, and liketerms as used herein, refers to the diacid derivative of the cyclicunsaturated acid anhydrides as defined herein that results from thehydrolysis of the anhydride group. A person skilled in the art willunderstand that the cyclic anhydride group will become non-cyclic uponhydrolysis.

Thus, examples of suitable diacid derivatives of cyclic unsaturated acidanhydrides include, but are not limited to, maleic acid,tetrahydrophthalic acid, methyltetrahydrophthalic acid,vinylhexahydrophthalic acid, endomethylenetetra-hydrophthalic acid,chlorendic acid, itaconic acid, citraconic acid, alkenyl succinic acidssuch as, for example, allyl succinic acid and dodecenyl succinic acid,norbornene acid and combinations thereof.

The diacid derivative of the cyclic unsaturated acid anhydride may bemaleic acid.

The crosslinking material may comprise the reaction product of areaction mixture comprising (ii) an ethylenically unsaturated monomer.The ethylenically unsaturated monomer may be any suitable ethylenicallyunsaturated monomer. Suitable ethylenically unsaturated monomers will bewell known to a person skilled in the art.

The ethylenically unsaturated monomer may comprise an acrylic monomer.Suitable acrylic monomers include, but are not limited to, alkyl(alk)acrylate, such as C₁ to C₆ alkyl (C₁ to C₆ alk)acrylate, forexample, C₁ to C₆ alkyl (meth)acrylate, and (alk)acrylic acid, such as(C₁ to C₆ alk)acrylic acid. The acrylic monomers may comprise afunctional group, such as an epoxy group. For example, the acrylicmonomers may comprise glycidyl methacrylate.

The terms “(alk)acrylate”, “(meth)acrylate” and like terms as usedherein are used conventionally and herein to refer to both alkacrylateand acrylate, such as methacrylate and acrylate.

Examples of suitable acrylic monomers include, but are not limited to,acrylic acid, methacrylic acid, methyl acrylate; methyl methacrylate;ethyl acrylate; ethyl methacrylate; propyl acrylate; propylmethacrylate; isopropyl methacrylate, isobutyl methacrylate, butylacrylate; butyl methacrylate, pentyl acrylate, pentyl methacrylate,isoamyl acrylate, isoamyl methacrylate, hexyl acrylate, hexylmethacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, decylacrylate, decyl methacrylate, isodecyl acrylate, isodecyl methacrylate,lauryl acrylate, lauryl methacrylate, octyl acrylate, octylmethacrylate, nonyl acrylate, nonyl methacrylate, isobornyl acrylate,isobornyl methacrylate, hydroxyethyl acrylate, hydroxyethylmethacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate,phenoxy ethyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexylmethacrylate, glycidyl methacrylate; ethylene glycol diacrylate;ethylene glycol dimethacrylate; 1,6-hexanediol diacrylate;1,6-hexanediol dimethacrylate; 4-hydroxybutyl acrylate; 4-hydroxybutylmethacrylate; allyl methacrylate; benzyl methacrylate; phosphate estersof 2-hydroxyethyl methacrylate; those sold under the trade name SIPOMERsuch as SIPOMER PAM-100, SIPOMER PAM-200 and SIPOMER PAM-300 (phosphateesters of polypropylene glycol monoacrylate commercially available fromSolvay); acrylamides such as, for example, acrylamide methacrylamide,N,N-dimethylacrylamide, N-ethylacrylamide, N-hydroxyethyl acrylamide,diacetone acrylamide, N,N-diethylacrylamide, N-isopropylacrylamide andN-isopropylmethacrylamide; 2-acrylamido-2-methyl-1-propanesulfonic acid;and combinations thereof. Any other acrylic monomers known to thoseskilled in the art could also be used.

The ethylenically unsaturated monomer may comprise a hydroxyl functionalmonomer, such as a hydroxyl functional acrylic monomer. Theethylenically unsaturated monomer may comprise a hydroxyl functionalalkyl(alk)acrylate, for example, hydroxyl functional C₁ to C₆ alkyl (C₁to C₆ alk)acrylate, such as hydroxyl functional C₁ to C₆ alkyl(meth)acrylate or hydroxyl functional C₁ to C₆ alkyl (C₁ to C₆alk)acrylate. Examples of suitable hydroxyl functional acrylicmonomer(s) include, but are not limited to, hydroxyethyl acrylate,hydroxyethyl methacrylate, hydroxymethyl acrylate, hydroxymethylmethacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,hydroxybutyl acrylate, hydroxybutyl methacrylate, hydroxypentylacrylate, hydroxypentyl acrylate, hydroxyhexyl methacrylate,hydroxyhexyl methacrylate, methyl 2-(hydroxymethyl)acrylate and/or ethyl2-(hydroxymethyl)acrylate. The ethylenically unsaturated monomer maycomprise hydroxyethyl acrylate and/or hydroxyethyl methacrylate, such ashydroxyethyl acrylate.

The hydroxyl functional ethylenically unsaturated monomer may compriseN-hydroxyethyl acrylamide, 2-hydroxyethyl vinyl ether, 4-hydroxybutylvinyl ether, 2-(2-hydroxyethyl) ethyl vinyl ether, and/orhydroxystyrene.

The hydroxyl functional ethylenically unsaturated monomer may comprisethe reaction product of (meth)acrylic acid with an epoxy (such asCardura E10) and/or the reaction product of glycidyl methacrylate with acarboxylic acid functional component (such as a benzoic acid, aliphaticacid).

The crosslinking material may comprise ≥2.5% hydroxyl functionalethylenically unsaturated monomer based on the total solid weight of themonomers from which the crosslinking material is formed, such as ≥5 wt%, or ≥7 wt %, or ≥10 wt %.

The crosslinking material may comprise ≥50% hydroxyl functionalethylenically unsaturated monomer based on the total solid weight of themonomers from which the crosslinking material is formed, such as ≤40 wt%, or ≤30 wt %, or ≤20 wt %.

The ethylenically unsaturated monomer may comprise a vinyl ethermonomer. Examples of suitable vinyl ether monomers include, but are notlimited to, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether,isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether,t-butyl vinyl ether, pentyl vinyl ether, cyclopentyl vinyl ether, hexylvinyl ether, cyclohexyl vinyl ether, 2-ethylhexyl vinyl ether,2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, 1,4-butanedioldivinyl ether, diethyleneglycol divinyl ether, triethyleneglycol divinylether, 1,4-cyclohexanedimethanol divinyl ether, 2-(2-hydroxyethyl) ethylvinyl ether, octyl vinyl ether, benzyl vinyl ether, phenyl vinyl ether,phenethyl vinyl ether, allyl vinyl ether and combinations thereof.

The ethylenically unsaturated monomer may comprise an additionalethylenically unsaturated monomer. Examples of suitable additionalethylenically unsaturated monomers include, but are not limited to, arylsubstituted ethylenically unsaturated monomers such as, for example,styrene, α-methylstyrene, vinyltoluene, chloromethylstyrene,4-hydroxystyrene, diglycidyloxymethylstyrene,2,4-diglycidyloxymethylstyrene, 2,5-diglycidyloxymethylstyrene,2,6-diglycidyloxymethylstyrene, 2,3,4-triglycidyloxymethylstyrene,2,3,5-triglycidyl oxime styrene, 2,3,6-triglycidyloxymethylstyrene and3,4,5-triglycidyloxymethylstyrene, 2,4,6-triglycidyloxymethylstyrene,ethylenically unsaturated nitriles such as, for example, acrylonitrileor methacrylonitrile, vinyl esters such as, for example, vinyl acetateand vinyl propionate, ethene, propene, 1-butene, 2-butene, 1-pentene,2-pentene, 1-hexene, 2-hexene, 3-hexene, 1-hetpene, 2-heptene,3-heptene, 1-octene, 2-octene, 3-octene, 4-octene, isobutylene, vinylchloride, butadiene, isoprene, chloroprene, N-vinyl monomers such as,for example, N-vinyl pyrrolidone, N-vinyl caprolactam and N-vinylacetamide, unsaturated fatty acid ester; allyl glycidyl ether, allylethyl ether and combinations thereof. The additional ethylenicallyunsaturated monomer(s) may comprise monomers, oligomers and/or polymersof the aforementioned monomers. For example, butadiene may be in theform of a monomer or may be in the form of polybutadiene.

The ethylenically unsaturated monomer(s) may comprise styrene, a vinylether monomer, vinyl acetate or combinations thereof.

The ethylenically unsaturated monomer(s) may comprise styrene, isobutylvinyl ether, vinyl acetate or combinations thereof.

The unsaturated acid anhydride and/or diacid derivative thereof maycomprise maleic anhydride and the ethylenically unsaturated monomer(s)may comprise styrene, isobutyl vinyl ether, vinyl acetate orcombinations thereof.

The unsaturated acid anhydride and/or diacid derivative thereof maycomprise maleic anhydride and the ethylenically unsaturated monomer(s)may comprise styrene, isobutyl vinyl ether, vinyl acetate and/or ahydroxyl functional monomer (such as hydroxyethyl (meth)acrylate).

The ethylenically unsaturated monomer(s) may comprise isobutyl vinylether.

The unsaturated acid anhydride and/or diacid derivative thereof maycomprise maleic anhydride and the ethylenically unsaturated monomer(s)may comprise isobutyl vinyl ether.

The crosslinking material may comprise at least 75 wt % of cyclicunsaturated acid anhydride and/or diacid derivative thereof, such asmaleic anhydride and/or maleic acid, such as at least 80 wt %, such asat least 85 wt %, such as at least 90 wt %, such as at least 95 wt % orat least 97 wt % or at least 98 wt % or at least 99 wt % or >99 wt %, orat least 99.1 wt %, or at least 99.5 wt % or at least 99.9 wt % or 100wt % cyclic unsaturated acid anhydride and/or diacid derivative thereof,based on the total solid weight of the monomers from which thecrosslinking material is formed.

The crosslinking material may comprise at least 80 wt % cyclicunsaturated acid anhydride and/or diacid derivative thereof, such asmaleic anhydride and/or maleic acid, based on the total solid weight ofthe monomers from which the crosslinking material is formed.

The crosslinking material may comprise at least 90 wt % cyclicunsaturated acid anhydride and/or diacid derivative thereof, such asmaleic anhydride and/or maleic acid, based on the total solid weight ofthe monomers from which the crosslinking material is formed.

The crosslinking material may comprise at least 95 wt % cyclicunsaturated acid anhydride and/or diacid derivative thereof, such asmaleic anhydride and/or maleic acid, based on the total solid weight ofthe monomers from which the crosslinking material is formed.

The crosslinking material may comprise at least 99 wt %, such as >99 wt% or at least 99.1 wt %, cyclic unsaturated acid anhydride and/or diacidderivative thereof, such as maleic anhydride and/or maleic acid, basedon the total solid weight of the monomers from which the crosslinkingmaterial is formed.

The crosslinking material may comprise up to 99 wt %, such as up to 95wt %, such as up to 90 wt %, such as up to 80 wt %, such as 70 wt %,cyclic unsaturated acid anhydride and/or diacid derivative thereof, suchas maleic anhydride and/or maleic acid, based on the total solid weightof the monomers from which the crosslinking material is formed.

For the avoidance of doubt, by ‘the total solid weight of the monomersfrom which the crosslinking material is formed’ as used herein is meantthe total solid weight of (i) a cyclic unsaturated acid anhydride and/ordiacid derivative thereof, (ii) an ethylenically unsaturated monomer,when present, and any additional monomer(s) present and does not include(iii) an alcohol, amine and/or thiol, when present.

The crosslinking material may be substantially free, may be essentiallyfree or may be completely free of styrene. By substantially free inrelation to styrene, is meant that the crosslinking material is formedfrom monomers which comprise less than 5 wt % of styrene based on thetotal weight of the monomers from which the crosslinking material isformed. By essentially free in relation to styrene, is meant that thecrosslinking material is formed from monomers which comprise less than 1wt % of styrene based on the total weight of the monomers from which thecrosslinking material is formed. By completely free in relation tostyrene, is meant that the crosslinking material is formed from monomerswhich comprise less than 0.01 wt % of styrene based on the total weightof the monomers from which the crosslinking material is formed. Thecrosslinking material may be formed from monomers which comprise no,i.e. 0 wt %, styrene based on the total weight of the monomers fromwhich the crosslinking material is formed.

The crosslinking material may comprise the reaction product of areaction mixture comprising (iii) an alcohol, amine thiol and/or water,such as with alcohol, amine and/or thiol.

The alcohol may be any suitable alcohol. Suitable alcohols will be knownto a person skilled in the art. The alcohol may be an aliphatic orcycloaliphatic C₁-C₂₀ alkanol, an aryl alcohol or combinations thereof.The alcohol may be a monohydric alcohol or a polyol, such as a diol,triol, tetraol etc., for example.

The alcohol may be an aliphatic or cycloaliphatic C₁-C₂₀ alkanol, suchas a C₁-C₁₀ alkanol, such as a C₁-C₆ alkanol, such as a C₁-C₄ alkanol,such as a C₁-C₃ alkanol, such as a C₁-C₂ alkanol, or even ethanol.Examples of suitable alcohols include, but are not limited to, methanol,ethanol, butoxy ethanol, 1-propanol, 2-propanol, 1,1-dimethyl1-propanol, methoxy propanol, 1-butanol, 2-butanol, 1-pentanol,2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2-ethyl1-hexanol, 2-butoxyethanol, heptanol, hydroxyethoxybenzene, dodecylalcohol, stearyl alcohol, oleyl alcohol, undecanol, cyclohexanol,methoxypropanol (such as Dowanol PM), alkylene glycols such as, forexample, ethylene glycol; propylene glycol; diethylene glycol;dipropylene glycol; triethylene glycol; tripropylene glycol; hexyleneglycol, polyethylene glycol, monoethers of glycols such as, for example,poly(ethylene glycol) methyl ether (MPEG) 500 and MPEG 350,polypropylene glycol and neopentyl glycol, hydrogenated bisphenol A,cyclohexanediol, propanediols such as, for example, 1,2-propanediol,1,3-propanediol, butyl ethyl propanediol, 2-methyl-1,3-propanediol and2-ethyl-2-butyl-1,3-propanediol, butanediols such as, for example,1,4-butanediol, 1,3-butanediol and 2-ethyl-1,4-butanediol, pentanediolssuch as, for example, trimethyl pentanediol and 2-methylpentanediol,cyclohexanedimethanol, hexanediols such as, for example, 1,6-hexanediol,caprolactonediol (for example, the reaction product of epsilon-caprolactone and ethylene glycol), polyether glycols such as, for example,poly(oxytetramethylene) glycol, trimethylol propane, pentaerythritol,di-pentaerythritol, trimethylol ethane, trimethylol butane, dimethylolcyclohexane, glycerol and combinations thereof.

The alcohol may be methanol, ethanol, propanol, butanol, butoxy ethanol,methoxy propanol or combinations thereof.

The alcohol may be an aryl alcohol. Examples of suitable aryl alcoholsinclude, but are not limited to, phenol, benzyl alcohol, phenethylalcohol, phenylpropyl alcohol, phenoxy ethanol, phenyl carbinol,methylphenyl carbinol, cresol, hydroxyalkylated bisphenols andcombinations thereof.

The amine may be any suitable amine. Suitable amines will be known to aperson skilled in the art. The amine may be an aliphatic orcycloaliphatic C₁-C₂₀ amine, such as a C₁-C₁₀ amine, such as a C₁-C₆amine, such as a C₁-C₄ amine, such as a C₁-C₃ amine, such as a C₁-C₂amine, or even ethylamine. The amine may be an aryl amine. The amine maybe a polyamine such as, for example, a diamine, triamine etc.

Examples of suitable amines include, but are not limited to,methylamine, ethylamine, propylamine, isopropylamine, butylamine,isobutylamine, t-butylamine, benzylamine, polyetheramines such as, forexample, those sold under the trade name JEFFAMINE (commerciallyavailable from Huntsman Corporation) or combinations thereof.

The thiol may be any suitable thiol. Suitable thiols will be known to aperson skilled in the art. Examples of suitable thiols include, but arenot limited to, methanethiol, ethanethiol, 1-propanethiol,2-propanethiol, 1-butanethiol, 2-butanethiol, beta-mercaptopropionicacids and/or esters, thiolglycolic acids and/or esters, thiophenol andcombinations thereof. The thiol may be a monothiol or a polythiol, suchas a dithiol, trithiol, tetrathiol etc., for example.

The alcohol, amine and/or thiol may have further functionality. Forexample, the alcohol may also have amine, acid, thiol, cyclic carbonate,hydroxy, epoxy or oxazoline functionality. For example, the amine mayalso have alcohol, acid, thiol, cyclic carbonate, hydroxy, epoxy oroxazoline functionality. For example, the thiol may also have amine,alcohol, acid, cyclic carbonate, hydroxy, epoxy or oxazolinefunctionality. It will be appreciated by a person skilled in the artthat, for example, an alcohol also having amine functionality may be thesame as an amine also having alcohol functionality. Examples of suitablealcohols, amines and/or thiols also having further functionalityinclude, but are not limited to, alkanolamines such as, for example,methanolamine, ethanolamine, methyl ethanolamine, ethyl ethanolamine,N-methyl ethanolamine, N-ethyl ethanolamine, 1-amino-2-propanol,3-amino-1-propanol, 4-amino-1-butanol, 1-amino-2-butanol,1-amino-3-butanol, dimethanolamine; diethanolamine, dipropanolamine,diisopropanolamine and methyl diethanolamine, hydroxyl and/oralkoxy-substituted oxazolines such as, for example, 2-propyl-4-methyoxyoxazoline, glycerol carbonate, glycidol, mercaptoethanol, glycolic acid,lactic acid, malic acid, tartaric acid, thiomalic acid and combinationsthereof.

The amine and/or thiol may be a hydroxy functional amine and/or thiol.The hydroxy functional amine and/or thiol may comprise a hydroxyl group.The hydroxy functional amine may be an alkanolamine for example analiphatic or cycloaliphatic C₁-C₂₀ alkanolamine, such as a C₁-C₁₀alkanolamine, such as a C₁-C₆ alkanolamine, such as a C₁-C₄alkanolamine, such as a C₁-C₃ alkanolamine, such as a C₁-C₂alkanolamine, or even ethanolamine. The hydroxyl functional amine may bean alkanolamine comprising two or more hydroxyl groups. For example, thehydroxy functional amine may be a dialkanolamine or a trialkanolamine.Each alkanol group may independently comprise C₁-C₂₀ alkanol, such asC₁-C₁₀ alkanol, or C₁-C₆ alkanol, or C₁-C₃ alkanol, such asdimethanolamine; diethanolamine, dipropanolamine, diisopropanolamine,such as diisopropanolamine.

The alcohol may comprise at least two hydroxyl groups.

The crosslinking material may comprise the reaction product of thereaction mixture comprising (iii) an alcohol, amine and/or thiol whereinthe amine and/or thiol comprises a hydroxy group and the alcoholcomprises at least two hydroxy groups.

The crosslinking material may comprise the reaction product of areaction mixture wherein ≥10%, such as ≥25 mol %, such as ≥4.0 mol %,such as 50 mol % of the cyclic unsaturated acid anhydride and/or diacidderivative thereof is reacted with an amine and/or thiol comprising ahydroxy group, and/or an alcohol comprising two or more hydroxy groups.

The use of alcohols, amines and/or thiols also having furtherfunctionality can allow for the crosslinking material to be dual-curingdue to the further functionality that remains available forcrosslinking, such that the crosslinking material may react with asuitable functional group of the binder and/or the suitable functionalgroup of the crosslinking material.

At least a portion of the cyclic unsaturated acid anhydride and/ordiacid derivative thereof may be reacted with the alcohol, amine thioland/or water, such as with alcohol, amine and/or thiol, when present. Itwill be appreciated by a person skilled in the art that reacting acyclic unsaturated acid anhydride and/or diacid derivative thereof withan alcohol, amine and/or thiol results in the esterification, amidationand/or thioesterification of one or each of the acid groups of saidcyclic unsaturated acid anhydride and/or diacid derivative thereof. Whena cyclic unsaturated acid anhydride and/or diacid derivative thereof isreacted with an alcohol, amine and/or thiol the monoester derivative maybe formed. However, alternatively, the diester derivative is formed. By‘monoester derivative’, and like terms as used herein, is meant that oneof the acid groups of the cyclic unsaturated acid anhydride and/ordiacid derivative thereof is reacted with an alcohol, amine and/or thiol(to form an ester, amide and/or thioester group). By ‘diesterderivative’, and like terms as used herein, is meant that both of theacid groups of the cyclic unsaturated acid anhydride and/or diacidderivative thereof is reacted with an alcohol, amine and/or thiol (toform an ester, amide and/or thioester group). When a cyclic unsaturatedacid anhydride is used, the reaction product may be obtained by reactingsaid alcohol, amine and/or thiol with the cyclic unsaturated acidanhydride under conditions which can affect the ring-opening reaction ofthe acid anhydride but which do not substantially cause apolyesterification, polyamidation and/or thioesterification reactionand/or formation of the diester, diamide and/or dithioester derivative.

The reaction of at least a portion of the cyclic unsaturated acidanhydride and/or diacid derivative thereof with the alcohol, amineand/or thiol may be monitored using Infrared (IR) spectroscopy.

At least a portion of the cyclic unsaturated acid anhydride may bereacted with water. It will be appreciated by a person skilled in theart that reacting a cyclic unsaturated acid anhydride with water resultsin the hydrolysis of said anhydride producing the diacid derivativethereof.

The crosslinking material may be formed by any suitable method. Forexample, the cyclic unsaturated acid anhydride and/or diacid derivativethereof may be caused to react to undergo polymerisation followed by atleast partial hydrolysis of the cyclic unsaturated acid anhydride and/orthe cyclic unsaturated acid anhydride and/or diacid derivative thereofmay be at least partially hydrolysed and then be caused to react toundergo polymerisation.

The cyclic unsaturated acid anhydride and/or diacid derivative thereofmay first be caused to react with the alcohol, amine, thiol and/orwater, when present, optionally followed, in a second step, by reactionwith the ethylenically unsaturated monomer, when present, or the cyclicunsaturated acid anhydride and/or diacid derivative thereof may first becaused to react with the ethylenically unsaturated monomer, whenpresent, followed, in a second step, by reaction with the alcohol,amine, thiol and/or water, when present.

Thus, there is also provided a method of producing a crosslinkingmaterial, the method comprising the steps of:

-   -   (a) reacting a cyclic unsaturated acid anhydride and/or diacid        derivative thereof with an alcohol, amine, thiol and/or water        wherein the cyclic unsaturated acid anhydride and/or diacid        derivative thereof is at least partially reacted with the        alcohol, amine, thiol and/or water (for example to at least        partially hydrolyse the cyclic unsaturated acid anhydride); and    -   (b) optionally, contacting the at least partially reacted cyclic        unsaturated acid anhydride and/or diacid derivative thereof with        an ethylenically unsaturated monomer; and    -   (c) causing a monomer composition comprising the at least        partially reacted cyclic unsaturated acid anhydride and/or        diacid derivative thereof, and optional ethylenically        unsaturated monomer to undergo polymerisation.

Thus, there is also provided a method of producing a crosslinkingmaterial, the method comprising the steps of:

-   -   (a) optionally contacting a cyclic unsaturated acid anhydride        and/or diacid derivative thereof with an ethylenically        unsaturated monomer;    -   (b) causing a monomer composition comprising cyclic unsaturated        acid anhydride and/or diacid derivative thereof, and optional        ethylenically unsaturated monomer to undergo polymerisation to        form a prepolymer; and    -   (c) reacting the prepolymer of step (b) with an alcohol, amine,        thiol and/or water, wherein the cyclic unsaturated acid        anhydride and/or diacid derivative thereof is at least partially        reacted with the alcohol, amine, thiol and/or water (for example        to at least partially hydrolyse the cyclic unsaturated acid        anhydride).

The step of causing the monomer composition to undergo polymerisationmay be performed by a free-radical polymerisation method. Suitablefree-radical polymerisation methods will be well known to a personskilled in the art. The free-radical polymerisation method may comprisea plurality of components, which may be referred to as a free-radicalpolymerisation reaction mixture. The free-radical polymerisationreaction mixture may comprise the monomer composition(s) defined above.

The free-radical polymerisation reaction mixture may further comprise afree radical initiator. Suitable initiators include, but are not limitedto, tertiary butyl perbenzoate; tert butylperoxy-3,5,5-trimethylhexanoate; tertiary butyl peroxy 2-ethylhexanoate; di tertiary butyl peroxide; tertiary butyl peracetate;tertiary butyl peroctoate; azo type initiators such as, for example,2,2′-Azobis(isobutyronitrile), 2,2′-Azobis(2-methylbutyronitrile),2,2′-Azobis(2,4-dimethyl valeronitrile) and2,2′-Azobis(4-methoxy-2,4-dimethyl valeronitrile); persulphateinitiators such as, for example, ammonium persulphate, sodiumpersulphate or potassium persulphate, hydrogen peroxide, tert-butylhydrogen peroxide, benzoin; and combinations thereof. The initiator maybe soluble in the free-radical polymerisation reaction mixture. Theinitiator may be soluble in the monomer composition. The initiator maybe soluble in a suitable solvent or mixture of solvents.

The free-radical polymerisation reaction mixture may comprise a solventor mixture of solvents. Suitable solvents will be well known to a personskilled in the art. Examples of suitable solvents include, but are notlimited to, water, alcohols such as, for example, ethanol, n-propanol,isopropanol, n-butanol, pentanol or hexanol; glycols such as, forexample, butyl glycol; glycol ethers such as, for example, 1-methoxypropan-2-ol di(propylene glycol) dimethyl ether or dipropylene glycolmono methyl ether; ketone solvents such as, for example, methyl isobutylketone or diacetone alcohol; ester solvents such as, for example,1-methoxy propanol acetate or butyl acetate; aromatic solvents such as,for example, toluene, xylene or those sold under the SOLVESSO® tradename such as SOLVESSO 100; and combinations thereof. The solvent maycomprise a mixture of solvents, such as n-butanol and butyl glycol. Itwill be appreciated by a person skilled in the art that the solvent ormixture of solvents may be chosen such that the monomer mixture issubstantially soluble in said solvent or mixture of solvents.

Free-radical polymerisation may be carried out at any suitabletemperature. Free-radical polymerisation may be carried out at anelevated temperature. Free-radical polymerisation may be carried out ata temperature from 60° C. to 200° C., such as from 80° C. to 200° C.,such as from 100° C. to 180° C., such as from 120° C. to 160° C., oreven from 130° C. to 150° C. Free-radical polymerisation may be carriedout at reflux.

The crosslinking material may be formed by providing a polymer formedfrom a cyclic unsaturated acid anhydride and/or diacid derivativethereof, optionally with an ethylenically unsaturated monomer(s) andoptionally reacting said polymer with an alcohol, amine, thiol and/orwater.

The crosslinking material may have an acid number of at least 100 mgKOH/g.

The crosslinking material may have an acid number of at least 200 mgKOH/g, such as at least 300 mg KOH/g, such as at least 400 mg KOH/g,such as at least 500 mg KOH/g, or even at least 600 mg KOH/g.

The crosslinking material may have an acid number up to 1,000 mg KOH/g,such as up to 975 mg KOH/g, such as up to 950 mg KOH/g, such as up to925 mg KOH/g, or even up to 900 mg KOH/g.

The crosslinking material may have an acid number from 100 to 1,000 mgKOH/g, such as from 200 to 975 mg KOH/g, such as from 300 to 950 mgKOH/g, such as from 400 to 925 mg KOH/g or even from 500 to 900 mg KOH/gor from 600 to 900 mg KOH/g.

The acid number of the crosslinking material is expressed on solids.

As reported herein, the acid number of the crosslinking material wasdetermined by titration with 0.1 M methanolic potassium hydroxidesolution by using a Metrohm 888 Titrando. The sample of polymer (0.1-3grams depending on acid number) was weighed accurately on a balance withaccuracy to weigh in milligrams into a conical flask and was thendissolved in 25 millilitres of a solvent mixture containing propyleneglycol and THF (20/80 vol/vol). The solution was titrated with thepotassium hydroxide solution using a Metrohm 888 Titrando.

The acid groups of the crosslinking material may be at least partiallyneutralised by contacting said crosslinking material with a neutraliser.Thus, the crosslinking material may comprise a neutraliser. Suitableneutralisers will be known to a person skilled in the art. Examples ofsuitable neutralisers include, but are not limited to, tertiary aminessuch as, for example, dimethylethanolamine (DMEA), trimethyl amine,N-methyl diethanol amine, N-ethyl N-methyl ethanol amine, N,N-dimethylethyl amine, N,N-dimethyl propyl amine, N,N-dimethyl 3-hydroxy-1-propylamine, N,N-dimeythylbenzyl amine, N,N-dimethyl 2-hydroxy-1-propyl amine,N,N-diethyl methyl amine, N,N-dimethyl 1-hydroxy-2-propyl amine,triethyl amine, tributyl amine, N,N-dimethyl dodecylamine, N-methylmorpholine; ammonia; hydrazine; metallic aluminium; metallic zinc;water-soluble oxides of the elements Li, Na, K, Mg, Ca, Fe(II) and Snap;water-soluble hydroxides of the elements Li, Na, K, Mg, Ca, Fe(II) andSnap; water-soluble carbonates of the elements Li, Na, K, Mg, Ca, Fe(II)and Sn(II); and combinations thereof. The neutraliser may comprise atertiary amine. The neutraliser may comprise dimethylethanolamine(DMEA).

The crosslinking material may have a hydroxyl number of ≥2 mg KOH/g,such as of ≥5 mg KOH/g, or of ≥10 mg KOH/g.

The crosslinking material may have a hydroxyl number of ≤230 mg KOH/g,such as ≤180 mg KOH/g, or ≤140 mg KOH/g.

The crosslinking material may have a hydroxyl number from 2 to 230 mgKOH/g, such as from 5 to 180 mg KOH/g, such as from 10 to 140 mg KOH/g.

The hydroxyl number is suitably expressed on solids.

As reported herein, the hydroxyl number was determined by esterificationof the sample with 10 mL of an acetylating reagent solution (1 aceticanhydride: 10 pyridine volumetric ratio) at 55° C. for 10 minutes using2 mL of 1-methylimidazole as a catalyst. After cooling the samplesolution, the excess acetic anhydride was converted to acetic acid byhydrolysis by adding a 20 mL solution of dimethylformamide, pyridine,and distilled water (3:1:1 volumetric ratio) to the above mixture. Theresulting solution containing excess acetic acid was titratedpotentiometrically with 0.5 N methanolic potassium hydroxide solution byusing a Metrohm 904 Titrando. The volume difference, in millilitres,between a blank determination (0 grams of sample) and the sampledetermination corresponds to the hydroxyl number of the sample. Thefollowing equation is used: hydroxyl number=[(volume of 0.5 N methanolicpotassium hydroxide used to neutralize blank)−(volume of 0.5 Nmethanolic potassium hydroxide used to neutralizesample)*0.5*56.1]/sample weight. The sample of polymer (0.1-3 gramsdepending on hydroxyl number) was weighed accurately on a balance withaccuracy to weigh in milligrams. If the polymer contains acidfunctionality then the hydroxyl number was corrected by the addition ofthe acid value with the measured hydroxyl value. Where the sample ofpolymer contained an alcoholic solvent, the hydroxyl number wascorrected by subtraction of the hydroxyl number corresponding to theweight percent of alcoholic solvent.

The crosslinking material may have any suitable glass transitiontemperature (Tg). The crosslinking material may have a Tg of at least 0°C., such as at least 20° C., such as at least 30° C., such as at least40° C., such as at least 50° C., such as at least 60° C., such as atleast 70° C., such as at least 80° C., such as at least 90° C., or evenat least 100° C. The crosslinking material may have a Tg of up to 300°C., such as up to 250° C., such as up to 225° C.

The crosslinking material may have a Tg from 0 to 300° C., such as from10 to 300° C., such as from 20 to 300° C., such as from 30 to 300° C.,such as from 40 to 300° C., such as from 50 to 300° C., such as from 60to 300° C., such as from 70 to 300° C., such as from 80 to 300° C., suchas from 90 to 300° C., or even from 100 to 300° C. The crosslinkingmaterial may have a Tg from 0 to 250° C., such as from 10 to 250° C.,such as from 20 to 250° C., such as from 30 to 250° C., such as from 40to 250° C., such as from 50 to 250° C., such as from 60 to 250° C., suchas from 70 to 250° C., such as from 80 to 250° C., such as from 90 to250° C., or even from 100 to 250° C. The crosslinking material may havea Tg from 0 to 225° C., such as from 10 to 225° C., such as from 20 to225° C., such as from 30 to 225° C., such as from 40 to 225° C., such asfrom 50 to 225° C., such as from 60 to 225° C., such as from 70 to 225°C., such as from 80 to 225° C., such as from 90 to 225° C., or even from100 to 225° C.

The crosslinking material may have a Tg of at least 50° C.

The crosslinking material may have a Tg of at least 100° C.

When the crosslinking material is formed from ethylenically unsaturatedmonomers comprising an acrylic monomer, the crosslinking material mayhave a Tg of at least 50° C.

When the crosslinking material is formed from ethylenically unsaturatedmonomers comprising an acrylic monomer, the crosslinking material mayhave a Tg of at least 100° C.

For the avoidance of doubt, in this context, ‘when the crosslinkingmaterial is formed from ethylenically unsaturated monomers comprising anacrylic monomer’ means that 100 wt % of the ethylenically unsaturatedmonomers are acrylic monomers (based on the total solid weight of themonomers).

When the crosslinking material is formed from ethylenically unsaturatedmonomers comprising styrene, the crosslinking material may have a Tg ofat least 50° C.

When the crosslinking material is formed from ethylenically unsaturatedmonomers comprising styrene, the crosslinking material may have a Tg ofat least 100° C.

When the crosslinking material is formed from ethylenically unsaturatedmonomers comprising a vinyl ether monomer, the crosslinking material mayhave a Tg of at least 0° C.

When the crosslinking material is formed from ethylenically unsaturatedmonomers comprising a vinyl ether monomer, the crosslinking material mayhave a Tg of at least 50° C.

For the avoidance of doubt, in this context, ‘when the crosslinkingmaterial is formed from ethylenically unsaturated monomers comprising avinyl ether monomer’ means that 100 wt % of the ethylenicallyunsaturated monomers are vinyl ether monomers (based on the total solidweight of the monomers).

When the crosslinking material is formed from ethylenically unsaturatedmonomers comprising a vinyl acetate monomer, the crosslinking materialmay have a Tg of at least 0° C.

When the crosslinking material is formed from ethylenically unsaturatedmonomers comprising a vinyl acetate monomer, the crosslinking materialmay have a Tg of at least 50° C.

When the crosslinking material is formed from ethylenically unsaturatedmonomers comprising a vinyl acetate monomer, the crosslinking materialmay have a Tg of at least 100° C.

For the avoidance of doubt, in this context, ‘when the crosslinkingmaterial is formed from ethylenically unsaturated monomers comprising avinyl ether monomer’ means that 100 wt % of the ethylenicallyunsaturated monomers are vinyl ether monomers (based on the total solidweight of the monomers).

As reported herein, the Tg was measured according to ASTM D6604-00(2013)(“Standard Practice for Glass Transition Temperatures of HydrocarbonResins by Differential Scanning calorimetry”. Heat-flux differentialscanning calorimetry (DSC), sample pans: aluminium, reference: blank,calibration: indium and mercury, sample weight: 10 mg, heating rate: 20°C./min). All values for Tg reported herein were measured in this way.

The crosslinking material may have any suitable number average molecularweight (Mn). The crosslinking material may have an Mn of at least 300 Da(Da=g/mole), such as at least 400 Da, or at least 500 Da.

The crosslinking material may have an Mn of up to 5,000 Da, such as upto 3,000 Da or up to 2,000 Da.

The crosslinking material may have an Mn of from 300 to 5,000 Da, suchas from 400 to 3,000 Da, such as from 500 to 2,000 Da.

As reported herein, the Mn was determined by gel permeationchromatography using a polystyrene standard according to ASTM D6579-11(“Standard Practice for Molecular Weight Averages and Molecular WeightDistribution of Hydrocarbon, Rosin and Terpene Resins by Size ExclusionChromatography”. RI detector; solvent: DMF/LiBr with phosphate acid asadditives; sample concentration: 10 mg/ml). Gel permeationchromatography was performed using a Waters 2695 separation module witha Waters 410 differential refractometer (RI detector). Dimethylformamide(DMF) with 0.05M Lithium bromide (LiBr) and 1% phosphate acid asadditive was used as the eluent at a flow rate of 0.8 ml min-1, and twoAgilent Polargel M (300×7.5 mm, 5 μm) columns were used for separationat a temperature of 50° C. Molecular weight averages of polymericsamples were measured relative to linear polystyrene standards of 580 to365,000 Da.

The crosslinking material may have any suitable weight average molecularweight (Mw).

The crosslinking material may have an Mw of at least 450 Da (Da=g/mole),such as at least 600 Da, or at least 800 Da.

The crosslinking material may have an Mw of up to 8,000 Da, such as upto 5,000 Da, or up to 4,000 Da.

The crosslinking material may have an Mw from 450 to 8,000 Da such asfrom 600 to 5,000 Da, such as from 800 to 4,000 Da.

As reported herein, the Mw was determined by gel permeationchromatography using a polystyrene standard according to ASTM D6579-11(“Standard Practice for Molecular Weight Averages and Molecular WeightDistribution of Hydrocarbon, Rosin and Terpene Resins by Size ExclusionChromatography”. RI detector; solvent: DMF/LiBr with phosphate acid asadditives; sample concentration: 10 mg/ml). Gel permeationchromatography was performed using a Waters 2695 separation module witha Waters 410 differential refractometer (RI detector). Dimethylformamide(DMF) with 0.05M Lithium bromide (LiBr) and 1% phosphate acid asadditive was used as the eluent at a flow rate of 0.8 ml min-1, and twoAgilent Polargel M (300×7.5 mm, 5 μm) columns were used for separationat a temperature of 50° C. Molecular weight averages of polymericsamples were measured relative to linear polystyrene standards of 580 to365,000 Da.

The crosslinking material may be substantially free, may be essentiallyfree or may be completely free of formaldehyde. “Substantially free”refers to crosslinking materials, or components thereof, containing lessthan 1000 parts per million (ppm) of formaldehyde. “Essentially free”refers to crosslinking materials, or components thereof, containing lessthan 100 ppm of any of formaldehyde. “Completely free” refers tocrosslinking materials, or components thereof, containing less than 20parts per billion (ppb) of formaldehyde.

The crosslinking material may be used in a coating composition.

The coating composition may comprise any suitable amount of thecrosslinking material. The coating composition may comprise at least 2wt %, or at least 3 wt %, such as at least 5 wt %, such as at least 8 wt% of the crosslinking material based on the total solid weight of thecoating composition.

The coating composition may comprise up to 90 wt %, such as up to 80 wt%, such as up to 70 wt %, such as up to 60 wt %, such as up to 50 wt %,such as up to 40 wt %, such as up to 30 wt %, or even 25 wt % of thecrosslinking material based on the total solid weight of the coatingcomposition.

The coating composition may comprise from 2 to 90 wt %, such as 3 to 90wt %, such as from 4 to 90 wt %, such as from 8 to 90 wt % of thecrosslinking material based on the total solid weight of the coatingcomposition. The coating composition may comprise from 2 to 80 wt %,such as 3 to 80 wt %, such as from 5 to 80 wt %, such as from 8 to 80 wt% of the crosslinking material based on the total solid weight of thecoating composition. The coating composition may comprise from 2 to 70wt %, such as 3 to 70 wt %, such as from 5 to 70 wt %, such as from 8 to70 wt % of the crosslinking material based on the total solid weight ofthe coating composition. The coating composition may comprise from 2 to60 wt %, such as 3 to 60 wt %, such as from 5 to 60 wt %, such as from 8to 60 wt % of the crosslinking material based on the total solid weightof the coating composition. The coating composition may comprise from 2to 50 wt %, such as 3 to 50 wt %, such as from 5 to 50 wt %, such asfrom 8 to 50 wt % of the crosslinking material based on the total solidweight of the coating composition. The coating composition may comprisefrom 2 to 40 wt %, such as 3 to 40 wt %, such as from 5 to 40 wt %, suchas from 8 to 40 wt % of the crosslinking material based on the totalsolid weight of the coating composition. The coating composition maycomprise from 2 to 30 wt %, such as 3 to 30 wt %, such as from 5 to 30wt %, such as from 8 to 30 wt % of the crosslinking material based onthe total solid weight of the coating composition.

The coating composition may comprise from 2 to 30 wt %, such as 3 to 30wt %, such as from 5 to 30 wt %, or even from 8 to 25 wt % of thecrosslinking material based on the total solid weight of the coatingcomposition.

The coating composition may comprise from 5 to 30 wt % of thecrosslinking material based on the total solid weight of the coatingcomposition.

When the coating composition is a packaging coating composition, such asa food and/or beverage packing coating composition, the coatingcomposition may comprise from 2 to 30 wt % of the crosslinking materialbased on the total solid weight of the coating composition. When thecoating composition is a packaging coating composition, such as a foodand/or beverage packing coating composition, the coating composition maycomprise from 5 to 30 wt % of the crosslinking material based on thetotal solid weight of the coating composition. When the coatingcomposition is a packaging coating composition, such as a food and/orbeverage packing coating composition, the coating composition maycomprise from 8 to 25 wt % of the crosslinking material based on thetotal solid weight of the coating composition.

Advantageously, the use of at least 2 wt % of the crosslinking materialbased on the total solid weight of the coating composition results in acoating composition having suitable acid resistance for packaging enduses. Advantageously, the use of up to 30 wt % of the crosslinkingmaterial based on the total solid weight of the coating compositionresults in a coating composition having suitable flexibility forpackaging end uses.

Thus, the present invention also provides a coating composition. Thecoating composition comprises a film-forming resin having a functionalgroup having an active hydrogen atom and a crosslinking material asdescribed herein.

The film-forming resin may have any suitable number-average molecularweight (Mn). The film-forming resin may have a Mn of 500 Daltons(Da=g/mole), such as 1,000. The film-forming resin may have a Mn of250,000 Daltons (Da=g/mole), such as 125,000 Da. The film-forming resinmay have a Mn of from 500 to 250,000 Daltons (Da=g/mole), such as from1,000 to 125,000 Da.

As reported herein, the Mn of the film-forming resin was determined bygel permeation chromatography using a polystyrene standard according toASTM D6579-11 (“Standard Practice for Molecular Weight Averages andMolecular Weight Distribution of Hydrocarbon, Rosin and Terpene Resinsby Size Exclusion Chromatography”. RI detector, solvent: unstabilisedTHF, retention time marker: toluene, sample concentration: 10 mg/ml).

The film-forming resin may have any suitable weight-average molecularweight (Mw). The film-forming resin may have a Mw of ≥1,000 Daltons(Da=g/mole), such as ≥2,000. The film-forming resin may have a Mw of≤500,000 Daltons (Da=g/mole), such as ≤250,000 Da. The film-formingresin may have a Mw of from 1,000 to 500,000 Daltons (Da=g/mole), suchas from 2,000 to 250,000 Da.

As reported herein, the Mw of the film-forming resin was determined bygel permeation chromatography using a polystyrene standard according toASTM D6579-11 (“Standard Practice for Molecular Weight Averages andMolecular Weight Distribution of Hydrocarbon, Rosin and Terpene Resinsby Size Exclusion Chromatography”. UV detector; 254 nm, solvent:unstabilised THF, retention time marker: toluene, sample concentration:2 mg/ml).

The film-forming resin may have any suitable acid value (AV) expressedon solids. The film-forming resin may have an AV expressed on solids of≥0 mg KOH/g, such as ≥20 mg KOH/g, or ≥30 mg KOH/g. The film-formingresin may have an AV expressed on solids of ≤400 mg KOH/g, such as ≤250mg KOH/g, or ≤150 mg KOH/g. The film-forming resin may have an AVexpressed on solids of from 0 to 400 mg KOH/g, such as from 20 to 250 mgKOH/g, or from 30 to 150 mg KOH/g.

As reported herein, the acid value (AV) of the film-forming resinexpressed on solids was determined by titration with 0.1 M methanolicpotassium hydroxide (KOH) solution. A sample of solid polymer (0.1 to 3g depending on acid number) was weighed accurately into a conical flaskand is dissolved, using light heating and stirring as appropriate, in 25ml of dimethyl formamide containing phenolphthalein indicator. Thesolution was then cooled to room temperature and titrated with the 0.1Mmethanolic potassium hydroxide solution. The resulting acid number isexpressed in units of mg KOH/g and is calculated using the followingequation:

${{Acid}{value}} = \frac{{titre}{of}{KOH}{{solution}({ml})} \times {molarity}{KOH}{{solution}(M)} \times 56.1}{{weight}{of}{solid}{{sample}(g)}}$

The film-forming resin may have any suitable glass transitiontemperature (Tg). The film-forming resin may have a Tg of ≥0° C. Thefilm-forming resin may have a Tg of ≤130° C., such as ≤75° C., such as≤50° C. The film-forming resin may have a Tg of from 0° C. to 130° C.,such as from 0° C. to 75° C., such as from 0° C. to 50° C.

The film-forming resin may comprise any suitable film-forming resinhaving a functional group having an active hydrogen atom. Functionalgroups having an active hydrogen include, but are not limited to,hydroxyl groups, thiol groups, carboxyl groups and/or amine groups. Thefunctional groups having an active hydrogen may comprise hydroxylgroups.

Thus, the film-forming resin may have hydroxyl functionality.

Thus, the coating composition may comprise a film-forming resin havinghydroxyl functionality.

Suitable examples of film-forming resins include, but are not limitedto, the following: polyester resins; acrylic resins; polyester graftacrylic (PGA) resins; polyvinyl chloride (PVC) resins; alkyd resins;polyurethane resins; polysiloxane resins; epoxy resins or combinationsthereof.

The film-forming resin may comprise a polyester graft acrylic (PGA)resin.

The film-forming resin may comprise an acrylic material. The acrylicmaterial may be any suitable acrylic material.

The film-forming resin may comprise a solution polymerised acrylicmaterial, an emulsion polymerised acrylic latex material or acombination thereof.

When the film-forming resin comprises a solution polymerised acrylicmaterial, the solution polymerised acrylic material may be any suitablesolution polymerised acrylic material. By “solution polymerised” andlike terms as used herein is meant a polymer that is formed by apolymerisation method whereby monomers are substantially dissolved in asolvent and polymerised. Once said monomers have been polymerised, theresultant solution polymerised acrylic material may be substantiallysoluble in said solvent.

The solution polymerised acrylic material may be formed from an acrylicmonomer. Suitable acrylic monomers are as described herein in relationto the ethylenically unsaturated monomers (ii).

The solution polymerised acrylic material may comprise pendant hydroxylgroups such that the solution polymerised acrylic material ishydroxyl-functional. The pendant hydroxyl groups may be provided in anysuitable manner. The pendant hydroxyl groups may be provided by monomershaving a pendant hydroxyl group. Suitable examples of monomers having apendant hydroxyl group include, but are not limited to, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl(meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl(meth)acrylate, 4-hydroxybutyl (meth)acrylate, ethyl-α-hydroxymethylacrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, monohydroxyethyl(meth)acrylate, p-hydroxyphenylethyl (meth)acrylate, 2,3-dihydroxypropyl(meth)acrylate, vinyl ethers, such as 2-hydroxyethyl vinyl ether,4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether andcyclohexane dimethanol monovinyl ether, for example, and combinationsthereof.

The acrylic monomer may comprise (meth)acrylic acid, methyl(meth)acrylate; butyl acrylate; and/or a hydroxyl functional acrylicmonomer, such as hydroxyethyl (meth)acrylate. The acrylic monomer maycomprise (meth)acrylic acid, methyl (meth)acrylate; butyl acrylate; anda hydroxyl functional acrylic monomer, such as hydroxyethyl(meth)acrylate. The acrylic monomer may comprise methacrylic acid,methyl methacrylate; butyl acrylate; and hydroxyethyl methacrylate.

The solution polymerised acrylic material may be formed from ≥10%hydroxyl functional acrylic monomer by total solid weight of themonomers from which the acrylic material is formed, such as ≥15 wt % or≥20%.

The solution polymerised acrylic material may be formed from ≥20%(meth)acrylic acid by total solid weight of the monomers from which theacrylic material is formed, such as ≥25 wt % or ≥30%.

The solution polymerised acrylic material may be formed from anadditional ethylenically unsaturated monomer. Suitable additionalethylenically unsaturated monomers include, but are not limited to, arylsubstituted ethylenically unsaturated monomers such as, for example,styrene; ethylenically unsaturated nitriles such as, for example,acrylonitrile or methacrylonitrile; and combinations thereof. Thependant hydroxyl groups may be provided by a reaction of the pendantfunctional groups of the acrylic resin with a further compound. Forexample, the pendant hydroxyl groups may be provided by the reaction ofpendant acid groups on the acrylic material with a further compoundhaving an oxirane group. For example, the pendant hydroxyl groups may beprovided by the reaction of pendant oxirane group(s) on the acrylicmaterial with a further compound having an acid group.

For the avoidance of doubt, an acrylic material in the context of thepresent invention is a material formed from an acrylic monomer (asdefined herein). The acrylic material may comprise any suitable amountof acrylic monomer(s). For example, the acrylic material may comprise atleast 10 wt %, such as at least 20 wt %, such as at least 30 wt %, suchas at least 40 wt %, such as at least 50 wt %, such as at least 60 wt %,such as at least 70 wt %, such as at least 80 wt %, or even at least 90wt % of acrylic monomer(s) based on the total solid weight of themonomers from which the acrylic material is formed. The acrylic materialmay comprise up to 100 wt % of acrylic monomer(s) based on the totalsolid weight of the monomers from which the acrylic material is formed.

The acrylic material may comprise from 10 to 100 wt % of acrylicmonomer(s) based on the total solid weight of the monomers from whichthe acrylic material is formed.

For example, the acrylic material may comprise up to 90 wt % of anadditional ethylenically unsaturated monomer based on the total solidweight of the monomers from which the acrylic material is formed. Theacrylic material may comprise up to 80 wt %, such as up to 70 wt %, suchas up to 60 wt %, such as up to 50 wt %, such as up to 40 wt %, such asup to 30 wt %, such as up to 20 wt %, or even up to 10 wt % of anadditional ethylenically unsaturated monomer based on the total solidweight of the monomers from which the acrylic material is formed. Theacrylic material may comprise no, i.e. 0 wt %, additional ethylenicallyunsaturated monomers based on the total solid weight of the monomersfrom which the acrylic material is formed.

The solution polymerised acrylic material may be substantially free, maybe essentially free or may be completely free of styrene. Bysubstantially free in relation to styrene, is meant that the solutionpolymerised acrylic material is formed from monomers which comprise lessthan 5 wt % of styrene based on the total weight of the monomers fromwhich the solution polymerised acrylic material is formed. Byessentially free in relation to styrene, is meant that the solutionpolymerised acrylic material is formed from monomers which comprise lessthan 1 wt % of styrene based on the total weight of the monomers fromwhich the solution polymerised acrylic material is formed. By completelyfree in relation to styrene, is meant that the solution polymerisedacrylic material is formed from monomers which comprise less than 0.01wt % of styrene based on the total weight of the monomers from which thesolution polymerised acrylic material is formed. The solutionpolymerised acrylic material may be formed from monomers which compriseno, i.e. 0 wt %, styrene based on the total weight of the monomers fromwhich the solution polymerised acrylic material is formed.

The solution polymerised acrylic material may be formed by a solutionpolymerisation method. Suitable solution polymerisation methods will bewell known to a person skilled in the art. The solution polymerisationmethod may comprise a plurality of components, which may be referred toas a solution polymerisation reaction mixture.

The solution polymerisation reaction mixture may comprise a solutionpolymerisation monomer component. The solution polymerisation monomercomponent may comprise an acrylic monomer as described herein. Thesolution polymerisation monomer component may optionally compriseadditional ethylenically unsaturated monomers as described herein.

The solution polymerisation reaction mixture may further comprise aninitiator. The initiator may be a free radical initiator. Suitableinitiators are as described herein in relation to the free-radicalpolymerisation method.

The solution polymerisation reaction mixture may comprise a solvent ormixture of solvents. Suitable solvents will be well known to a personskilled in the art. Examples of suitable solvents are as describedherein in relation to the free-radical polymerisation method. It will beappreciated by a person skilled in the art that the solvent or mixtureof solvents may be chosen such that the monomer mixture is substantiallysoluble in said solvent or mixture of solvents.

The solution polymerisation monomer component is caused to undergopolymerisation in the solvent or mixture of solvents to form thesolution polymerised acrylic material. Thus, the solution polymerisationof the solution polymerisation monomer component may be carried out as afree radical initiated solution polymerisation in a solvent or mixtureof solvents.

Solution polymerisation may be carried out at any suitable temperature.Suitable temperatures are as described herein in relation to thefree-radical polymerisation method. Solution polymerisation may becarried out at reflux.

The solution polymerised acrylic material may comprise pendant acidgroups. The acid groups of the solution polymerised acrylic material, ifpresent, may be at least partially neutralised. The acid groups of thesolution polymerised acrylic material, if present, may be at leastpartially neutralised by contacting said solution polymerised acrylicmaterial with a neutraliser. Thus, the solution polymerised acrylicmaterial may comprise a neutraliser. Suitable neutralisers will be wellknown to a person skilled in the art. Examples of suitable neutralisersinclude, but are not limited to, tertiary amines such as, for example,dimethylethanolamine (DMEA), trimethyl amine, methyl diethanol amine,ethyl methyl ethanol amine, dimethyl ethyl amine, dimethyl propyl amine,dimethyl 3-hydroxy-1-propyl amine, dimeythylbenzyl amine, dimethyl2-hydroxy-1-propyl amine, diethyl methyl amine, dimethyl1-hydroxy-2-propyl amine, triethyl amine, tributyl amine, N-methylmorpholine; ammonia; hydrazine; metallic aluminium; metallic zinc;water-soluble oxides of the elements Li, Na, K, Mg, Ca, Fe(II) andSn(II); water-soluble hydroxides of the elements Li, Na, K, Mg, Ca,Fe(II) and Snap; water-soluble carbonates of the elements Li, Na, K, Mg,Ca, Fe(II) and Snap; and combinations thereof. The neutraliser maycomprise a tertiary amine. The neutraliser may comprisedimethylethanolamine (DMEA).

The solution polymerised acrylic material may be substantially dissolvedand/or dispersed in water. The solution polymerised acrylic material maybe substantially dissolved in water. The solution polymerised acrylicmaterial may be substantially dissolved and/or dispersed in waterbefore, during or after the addition of neutraliser. The solutionpolymerised acrylic material may be substantially dissolved and/ordispersed in water during the addition of neutraliser. Therefore, thesolution polymerised acrylic material may be formed in a solvent andsubsequently substantially dissolved and/or dispersed in water. Thesolution polymerised acrylic material may be formed in a solvent andsubsequently substantially dissolved in water. The solution polymerisedacrylic material has sufficient functionality such that it may besubstantially dissolved in water.

The solution polymerised acrylic material may have any suitablenumber-average molecular weight (Mn). The solution polymerised acrylicmaterial may have Mn of 500 Daltons (Da=g/mole), such as ≥1,000 Da, or≥2,000 Da or ≥4,000 Da. The solution polymerised acrylic material mayhave a Mn of ≤250,000 Daltons (Da=g/mole), such as ≤125,000 Da or≤50,000 Da or ≤20,000 Da or ≤10,000 Da. The solution polymerised acrylicmaterial may have a Mn of from 500 to 250,000 Daltons (Da=g/mole), suchas from 1,000 to 125,000 Da or from 2,000 to 50,000 Da, such as from2,000 to 20,000 Da, or even from 4,000 to 10,000 Da.

The solution polymerised acrylic material may have any suitableweight-average molecular weight (Mw). The solution polymerised acrylicmaterial may have Mw of ≥1,000 Daltons (Da=g/mole), such as ≥2,000 Da,or ≥1,000 Da or ≥8,000 Da. The solution polymerised acrylic material mayhave a Mw of ≤500,000 Daltons (Da=g/mole), such as ≤250,000 Da or≤100,000 Da or ≤40,000 Da or ≤20,000 Da. The solution polymerisedacrylic material may have a Mw of from 1,000 to 500,000 Daltons(Da=g/mole), such as from 2,000 to 250,000 Da or from 4,000 to 100,000Da, such as from 4,000 to 40,000 Da, or even from 8,000 to 20,000 Da.

When the film-forming resin comprises an emulsion polymerised acryliclatex material, the emulsion polymerised acrylic latex material may beany suitable emulsion polymerised acrylic latex material. By “emulsionpolymerised” and like terms as used herein is meant a polymer that isformed by a polymerisation method which starts with an emulsioncomprising, at least, water and a monomer that is substantiallyinsoluble in the said water. The monomer may form an oil phase in theaqueous phase (water). The resultant emulsion polymerised acrylic latexmaterial is in the form of a stable emulsion of polymer microparticlesin the aqueous medium.

The emulsion polymerised acrylic latex material may be formed from anacrylic monomer(s). Suitable acrylic monomers are as described herein inrelation to the solution polymerised acrylic material.

The emulsion polymerised acrylic material may comprise pendant hydroxylgroups such that the solution polymerised acrylic material ishydroxyl-functional. The pendant hydroxyl groups may be provided in anysuitable manner. The pendant hydroxyl groups may be provided by amonomer having a pendant hydroxyl group. Suitable examples of a monomerhaving a pendant hydroxyl group are as described herein in relation tothe ethylenically unsaturated monomers (ii). The pendant hydroxyl groupsmay be provided by a reaction of the pendant functional groups of theacrylic resin with a further compound. For example, the pendant hydroxylgroup may be provided by the reaction of a pendant acid group on theacrylic material with a further compound having an oxirane group. Forexample, the pendant hydroxyl group may be provided by the reaction of apendant oxirane group on the acrylic material with a further compoundhaving an acid group.

The emulsion polymerised acrylic latex material may be formed from anadditional ethylenically unsaturated monomer. Suitable additionalethylenically unsaturated monomer are as described herein in relation tothe solution polymerised acrylic material. The additional ethylenicallyunsaturated monomer may comprise styrene.

The emulsion polymerised acrylic latex material may be formed frommonomers comprising ethyl acrylate, styrene, glycidyl methacrylate,acrylic acid, butyl acrylate or combinations thereof.

The emulsion polymerised acrylic latex material may be substantiallyfree, may be essentially free or may be completely free of styrene.Substantially free, essentially free and completely free in relation tostyrene is as described herein in relation to the solution polymerisedacrylic material.

The emulsion polymerised acrylic latex material may comprise an aqueousdispersion of said emulsion polymerised acrylic latex material.

The emulsion polymerised acrylic latex material is may be formed by anemulsion polymerisation method. Suitable emulsion polymerisation methodswill be well known to a person skilled in the art. The emulsionpolymerisation method may comprise a plurality of components, which maybe referred to as an emulsion polymerisation reaction mixture.

The emulsion polymerisation reaction mixture may comprise an emulsionpolymerisation monomer component. The emulsion polymerisation monomercomponent may comprise an acrylic monomer as described herein. Theemulsion polymerisation monomer component may optionally compriseadditional ethylenically unsaturated monomers as described herein.

The emulsion polymerisation monomer component may be substantiallyhydrophobic. For example, the monomers may have a partition coefficientof at least 1 (one), such as at least 1.25, such as at least 1.5, suchas at least 2, or even at least 2.5. For the avoidance of doubt, it isthe monomers present overall and not each individual monomer present inthe emulsion polymerisation monomer component that should have apartition coefficient of at least 1 (one). The use of an emulsionpolymerisation monomer component having a partition coefficient of atleast 1 (one), may result in an emulsion polymerised acrylic latexmaterial that displays lower agglomeration than may be expected.

The emulsion polymerisation reaction mixture may further comprise aninitiator. Suitable initiators are as described herein in relation tothe free-radical polymerisation method. The initiator may compriseammonium persulphate, hydrogen peroxide, benzoin or combinationsthereof.

The emulsion polymerisation reaction mixture may comprise water.

The monomer component of the emulsion polymerisation reaction mixturemay be caused to undergo polymerisation in the water to form theemulsion polymerised acrylic latex material. Thus, the polymerisation ofthe monomer component of the emulsion polymerisation reaction mixturemay be carried out as a free radical initiated emulsion polymerisationin water. The monomer component of the emulsion polymerisation reactionmixture may form an oil phase in the water.

The emulsion polymerisation reaction mixture may comprise a buffer.Suitable buffers will be well known to a person skilled in the art. Thebuffer may be operable to act as a hydrogen ion acceptor. Examples ofsuitable buffers include, but are not limited to, sodium bicarbonate.

The emulsion polymerisation reaction mixture may comprise a surfactant.The surfactant may be an anionic, cationic or non-ionic type stabilizer.Suitable examples of anionic surfactants include, but are not limitedto, alkyl sulphates such as, for example, sodium dodecyl sulphate orsodium polyoxy ethylene alkyl ether sulphate; aryl sulphonates such as,for example, sodium dodecylbenzene sulphonate; sulphosuccinates such as,for example, sodium diisobutyl sulpho succinate, sodium dioctyl sulphosuccinate and sodium di cyclohexyl sulpho succinate; and combinationsthereof. Suitable examples of non-ionic emulsifiers include, but are notlimited to, fatty alcohol ethoxylates such as, for example polyethyleneglycol mono lauryl ether; fatty acid ethoxylates such as, for example,polyethylene glycol mono stearate or polyethylene glycol mono laurate;polyether block polymers such as, for example, polyethyleneglycol/polypropylene glycol block polymers also known as pluronics,commercial products of this type include Tergitol® XJ, XH or XDcommercially available from Dow Chemical; and combinations thereof.Suitable examples of cationic emulsifiers include, but are not limitedto, amine salts such as, for example, cetyl trimethyl ammonium chlorideor benzyl dodecyl dimethyl ammonium bromide; and combinations thereof.It will be appreciated by a person skilled in the art that mixtures ofanionic and cationic emulsifiers may not be desirable.

The surfactant may be polymeric. The surfactant may be polymerisablewith the emulsion polymerised acrylic latex material. For example, thesurfactant may be polymerisable with the monomers that form the emulsionpolymerised acrylic latex material.

The emulsion polymerisation reaction mixture may be substantially free,may be essentially free or may be completely free of surfactant. Bysubstantially free in relation to surfactants, is meant that theemulsion polymerisation reaction mixture comprises less than 5 wt % ofsurfactant based on the total weight of the emulsion polymerisationreaction mixture. By essentially free in relation to surfactants, ismeant that the emulsion polymerisation reaction mixture comprises lessthan 1 wt % of surfactant based on the total weight of the emulsionpolymerisation reaction mixture. By completely free in relation tosurfactants, is meant that the emulsion polymerisation reaction mixturecomprises less than 0.01 wt % of surfactant based on the total weight ofthe emulsion polymerisation reaction mixture. The emulsionpolymerisation reaction mixture may comprise no, i.e. 0 wt %,surfactant.

The emulsion polymerisation reaction mixture may comprise a neutraliser.Suitable neutralisers are as described herein in relation to thesolution polymerised acrylic material. A neutraliser may be added to atleast of portion of the emulsion polymerisation monomer component. Aneutraliser may be added to at least a portion of the emulsionpolymerisation monomer component prior to the polymerisation reaction,i.e. prior to the emulsion polymerisation monomer component contactingthe initiator.

Emulsion polymerisation may be carried out in a suitable reactionvessel. The emulsion polymerisation monomer component, initiator and/orwater of the emulsion polymerisation reaction mixture may be added tothe reaction vessel in any suitable order. For example, the water may beadded to the reaction vessel before the emulsion polymerisation monomercomponent and/or initiator are added to the reaction vessel. Theinitiator may be added to the reaction vessel before the emulsionpolymerisation monomer component. The emulsion polymerisation monomercomponent and/or initiator may be added to the reaction vessel over anysuitable period of time. The emulsion polymerisation monomer componentand/or initiator may be added to the reaction vessel over a time periodof from 0 to 24 hours, such as from 30 minutes to 12 hours, such as from1 hour to 10 hours, such as from 2 hours to 10 hours, or even from 2 to6 hours. The emulsion polymerisation monomer component and/or initiatormay be added to the reaction vessel over a time period of 3 to 5 hours,such as 4 to 5 hours. For the avoidance of doubt, when the emulsionpolymerisation monomer component and/or initiator are added over a timeperiod of 0 hours, all of the emulsion polymerisation monomer componentand/or initiator are added at the same time (i.e. in a single addition).Adding the emulsion polymerisation monomer component over theaforementioned time periods may result in an emulsion polymerisedacrylic latex material that displays lower agglomeration than may beexpected.

The emulsion polymerisation monomer component may be added at anysuitable rate during the time period for addition of the emulsionpolymerisation monomer component. The emulsion polymerisation monomercomponent may be added at a constant rate or the emulsion polymerisationmonomer component may be added at a variable rate during the time periodfor addition of the emulsion polymerisation monomer component. Theemulsion polymerisation monomer component may be added dropwise. By theterm ‘dropwise’ and like terms as used herein is meant, unless specifiedotherwise, that the emulsion polymerisation monomer component is addedat a rate of from 0.05 to 1.0 wt %/minute over a period of time, T,based on the total solid weight of the monomers in the emulsionpolymerisation monomer component. The emulsion polymerisation monomercomponent may be added at a rate which results in a low level of freemonomer in the emulsion polymerisation reaction mixture. The emulsionpolymerisation monomer component may be added at a rate which reduces orsubstantially prevents the monomers of the emulsion polymerisationmonomer component from being insoluble in the emulsion polymerisationreaction mixture. In other words, the emulsion polymerisation monomercomponent may be added at a suitable rate such that the monomers of theemulsion polymerisation monomer component are and/or remainsubstantially dissolved in the emulsion polymerisation reaction mixture.Adding the emulsion polymerisation monomer component dropwise may resultin a low level of free monomer in the emulsion polymerisation reactionmixture such that the emulsion polymerisation reaction results in anemulsion polymerised acrylic latex material that displays loweragglomeration than may be expected.

The emulsion polymerisation monomer component may be added at a variablerate during the time period for addition of the emulsion polymerisationmonomer component. The emulsion polymerisation monomer component may beadded at a slower rate initially and then at an increasingly faster rateduring the time period for addition of the emulsion polymerisationmonomer component. For example, the emulsion polymerisation monomercomponent may initially be added at a rate of from 0.05 to 0.50 wt%/minute, such as from 0.1 to 0.25 wt %/minute, such as from 0.1 to 0.2wt %/minute, or even from 0.15 to 0.2 wt %/minute based on the totalsolid weight of the monomers in the emulsion polymerisation monomercomponent. The emulsion polymerisation monomer component maysubsequently be added at a rate of from 0.1 to 1 wt %/minute, such asfrom 0.2 to 0.5 wt %/minute, such as from 0.2 to 0.4 wt %/minute, oreven from 0.3 to 0.4 wt %/minute based on the total solid weight of themonomers in the emulsion polymerisation monomer component. The emulsionpolymerisation monomer component may subsequently be added at a rate offrom 0.2 to 2 wt %/minute, such as from 0.4 to 1.0 wt %/minute, such asfrom 0.4 to 0.8 wt %/minute, or even from 0.5 to 0.8 wt %/minute basedon the total solid weight of the monomers in the emulsion polymerisationmonomer component. For example, the emulsion polymerisation monomercomponent may initially be added at a rate of from 0.05 to 0.50 wt%/minute, such as from 0.1 to 0.25 wt %/minute, such as from 0.1 to 0.2wt %/minute, or even from 0.15 to 0.2 wt %/minute based on the totalsolid weight of the monomers in the emulsion polymerisation monomercomponent for a time period from 1 minute to 3 hours, such as from 15minutes to 2 hours, such as from 30 minutes to 90 minutes, or even for atime period of 1 hour. The emulsion polymerisation monomer component maysubsequently be added at a rate of from 0.1 to 1 wt %/minute, such asfrom 0.2 to 0.5 wt %/minute, such as from 0.2 to 0.4 wt %/minute, oreven from 0.3 to 0.4 wt %/minute based on the total solid weight of themonomers in the emulsion polymerisation monomer component for a timeperiod from 1 minute to 3 hours, such as from 15 minutes to 2 hours,such as from 30 minutes to 90 minutes, or even for a time period of 1hour. The emulsion polymerisation monomer component may subsequently beadded at a rate of from 0.2 to 2 wt %/minute, such as from 0.4 to 1.0 wt%/minute, such as from 0.4 to 0.8 wt %/minute, or even from 0.5 to 0.8wt %/minute based on the total solid weight of the monomers in theemulsion polymerisation monomer component for a time period from 1minutes to 6 hours, such as from 30 minutes to 4 hours, such as from 1hour to 3 hours, or even for a time period of 2 hours.

Emulsion polymerisation may be carried out at any suitable temperature.Emulsion polymerisation may be carried out at a temperature from 20° C.to 150° C., such as from 40° C. to 120° C., such as from 50° C. to 100°C., such as from 60° C. to 95° C., or even from 70° C. to 90° C. Thetemperature may be held constant throughout the emulsion polymerisationprocess.

The emulsion polymerised acrylic latex material may comprise pendantacid groups. The acid groups of the emulsion polymerised acrylic latexmaterial may be at least partially neutralised. The acid groups of theemulsion polymerised acrylic latex material may be at least partiallyneutralised by contacting said acid-functional emulsion polymerisedacrylic latex material with a neutraliser. Thus, the emulsionpolymerised acrylic latex material may comprise a neutraliser. Suitableneutralisers are as described herein in relation to the solutionpolymerised acrylic material. The neutraliser may comprise a tertiaryamine. The neutraliser may comprise dimethylethanolamine (DMEA).

The emulsion polymerised acrylic latex material may be in a core/shellarrangement. The core/shell arrangement may be internally crosslinked.

The shell may be formed from a plurality of components, which may bereferred to as a shell mixture. The shell mixture may comprise anacrylic monomer as described herein. The shell mixture may optionallycomprise additional ethylenically unsaturated monomers as describedherein.

The shell mixture may comprise acrylic acid, ethyl acrylate, styrene orcombinations thereof.

The shell mixture may further comprise an initiator. Suitable initiatorsare as described herein in relation to the solution polymerised acrylicmaterial.

The shell mixture may be caused to undergo polymerisation to form ashell polymer. The polymerisation of the shell mixture may be carriedout as a free radical initiated solution polymerisation in a solvent ormixture of solvents. The solvents which may be used in this processinclude, but are not limited to, alcohols such as n-butanol, pentanol orhexanol; or glycol ethers such as 2-butoxy ethanol, 1-methoxypropan-2-ol or dipropylene glycol mono methyl ether. Polymerisation maybe carried out at an elevated temperature. The polymerisation may becarried out in the range 80° C. to 150° C. The polymerisation can beeffectively carried out by adding the shell mixture, over a set timeperiod, to the solvent mixture. The shell mixture may be caused toundergo polymerisation to form a shell polymer prior to contact withcomponents of the core mixture.

Where the shell mixture comprises an ethylenically unsaturatedcarboxylic acid, the shell polymer will have pendant carboxylic acidfunctional groups. This may be referred to as a carboxylic acidfunctional shell polymer.

The carboxylic acid functional shell polymer may be contacted with abase to form a water dispersible salt. The carboxylic acid functionalityin the carboxylic acid functional shell polymer may be at least partlyneutralised with the base. At least 10% of the available carboxylic acidgroups may be neutralised. Substantially all of the available carboxylicacid groups may be neutralised by the base. The base used for thisneutralisation may comprise an amine functional material, or a mixtureof amine functional materials. Examples of suitable amine functionalmaterials include ammonia, triethylamine, diethylamine, trimethylamineand morphline or hydroxy amine materials such as ethanol amine, N-methylethanolamine and N,N-dimethyl ethanolamine.

The shell polymer may be dispersed in aqueous medium. In this manner, anaqueous dispersion or solution of the shell polymer may be formed.

The shell mixture may be caused to undergo polymerisation to form ashell polymer by emulsion polymerisation in an aqueous medium, therebyforming an aqueous dispersion or solution of the shell polymer.

The core may be formed from plurality of components, which may bereferred to as a core mixture. The core mixture comprises an acrylicmonomer as described herein. The core mixture may optionally compriseadditional ethylenically unsaturated monomers as described herein.

The core mixture may comprise ethyl acrylate, styrene, glycidylmethacrylate or combinations thereof.

The polymer formed from the shell mixture, such as an aqueous dispersionthereof, may serve as a dispersant for a subsequent polymerisation,which may be a polymerisation of ethylenically unsaturated monomermixture, such as the core mixture.

The core mixture may further comprise an initiator. Suitable initiatorsare as described herein in relation to the free-radical polymerisedacrylic material.

The core mixture may be caused to undergo polymerisation at atemperature in the range from 30° C. to 99° C., such as in the rangefrom 50° C. to 95° C., such as in the range from 80° C. to 90° C.Polymerisation of the core mixture may occur in the presence of thepolymer formed by polymerisation of the shell mixture to thereby form acore/shell polymer, such as by emulsion polymerisation. Polymerisationmay be carried out by adding the core mixture, at a controlled rate overa period of time, to an aqueous dispersion of shell polymer. During thepolymerisation the mixture may be mixed, such as by stirring and thetemperature may be held generally constant.

Other methods to polymerise the core mixture include, but are notlimited to, mixing all or part of the core ethylenically unsaturatedsubstances with the aqueous dispersion of shell polymer and then addingthe remaining core components, including initiator, to the resultingmixture over a set period of time. Suitable temperatures for this typeof process may be in the range 50° C. to 95° C.

The core/shell latex may be internally crosslinked. The core/shell latexmay be crosslinked in any suitable manner. For example, a functionalgroup of the shell may be crosslinked to a functional group of the core.For example, the core/shell latex may be crosslinked by reaction with acrosslinking agent. Examples of suitable crosslinking agents include,but are not limited to, polyacids, polyepoxies, polyamines,alkoxysilanes, keto/hydrazides, polycarbodiimides, polyoxazolines,polyaziridines and combinations thereof.

For the core/shell latex composition the ratio of the core mixture(monomers and initiator) to shell mixture (monomers and initiator) maybe from 20:80 to 90:10 by weight. The ratio of the core mixture to shellmixture may be from 60:40 to 80:20 by weight, such as from 70:30 to75:25 by weight. The emulsion polymerised latex acrylic material mayhave any suitable number-average molecular weight (Mn). The emulsionpolymerised latex acrylic material may have Mn of 1,000 Daltons(Da=g/mole), such as ≥2,000 Da, or ≥4,000 Da or ≥8,000 Da. The emulsionpolymerised latex acrylic material may have a Mn of ≤350,000 Daltons(Da=g/mole), such as ≤300,000 Da or ≤250,000 Da or ≤200,000 Da or≤150,000 Da. The solution polymerised acrylic material may have a Mn offrom 1,000 to 350,000 Daltons (Da=g/mole), such as from 2,000 to 300,000Da or from 4,000 to 250,000 Da, such as from 4,000 to 200,000 Da, oreven from 8,000 to 150,000 Da.

The emulsion polymerised latex acrylic material may have any suitableweight-average molecular weight (Mw). The emulsion polymerised latexacrylic material may have Mw of 2,000 Daltons (Da=g/mole), such as≥4,000 Da, or ≥8,000 Da or ≥16,000 Da. The emulsion polymerised latexacrylic material may have a Mw of ≤700,000 Daltons (Da=g/mole), such as≤600,000 Da or ≤500,000 Da or ≤400,000 Da or ≤300,000 Da. The emulsionpolymerised latex acrylic material may have a Mw of from 2,000 to700,000 Daltons (Da=g/mole), such as from 4,000 to 600,000 Da or from8,000 to 500,000 Da, such as from 8,000 to 400,000 Da, or even from16,000 to 300,000 Da.

The film-forming resin may comprise an emulsion polymerised latexacrylic material.

The film-forming resin may comprise a solution polymerised acrylicmaterial.

The coating composition may comprise any suitable amount of thefilm-forming resin, such as emulsion polymerised latex acrylic materialand/or solution polymerised acrylic material. The coating compositionmay comprise at least 10 wt %, such as at least 20 wt %, such as atleast 30 wt %, such as at least 40 wt %, such as at least 50 wt %, suchas at least 60 wt %, such as at least 70 wt %, or even at least 75 wt %of the film-forming resin based on the total solid weight of the coatingcomposition. The coating composition may comprise up to 98 wt %, such asup to 97 wt %, such as up to 95 wt %, such as up to 90 wt %, such as upto 85 wt % or even up to 80 wt % of the film-forming resin based on thetotal solid weight of the coating composition.

The coating composition may comprise at least 50 wt % of thefilm-forming resin, such as at least 60 wt %, such as at least 70 wt %,or even at least 75 wt % of the film-forming resin based on the totalsolid weight of the coating composition.

The coating composition may comprise from 10 to 98 wt %, such as from 20to 98 wt %, such as from 30 to 98 wt %, such as from 40 to 98 wt %, suchas from 50 to 98 wt %, such as from 60 to 98 wt %, such as from 70 to 98wt %, or even from 75 to 98 wt % of the film-forming resin based on thetotal solid weight of the coating composition. The coating compositionmay comprise from 10 to 97 wt %, such as from 20 to 97 wt %, such asfrom 30 to 97 wt %, such as from 40 to 97 wt %, such as from 50 to 97 wt%, such as from 60 to 97 wt %, such as from 70 to 97 wt %, or even from75 to 97 wt % of the film-forming resin based on the total solid weightof the coating composition. The coating composition may comprise from 10to 95 wt %, such as from 20 to 95 wt %, such as from 30 to 95 wt %, suchas from 40 to 95 wt %, such as from 50 to 95 wt %, such as from 60 to 95wt %, such as from 70 to 95 wt %, or even from 75 to 95 wt % of thefilm-forming resin based on the total solid weight of the coatingcomposition. The coating composition may comprise from 10 to 90 wt %,such as from 20 to 90 wt %, such as from 30 to 90 wt %, such as from 40to 90 wt %, such as from 50 to 90 wt %, such as from 60 to 90 wt %, suchas from 70 to 90 wt %, or even from 75 to 90 wt % of the film-formingresin based on the total solid weight of the coating composition. Thecoating composition may comprise from 10 to 80 wt %, such as from 20 to80 wt %, such as from 30 to 80 wt %, such as from 40 to 80 wt %, such asfrom 50 to 80 wt %, such as from 60 to 80 wt %, such as from 70 to 80 wt%, or even from 75 to 80 wt % of the film-forming resin based on thetotal solid weight of the coating composition.

The coating composition may comprise from 70 to 98 wt % of thefilm-forming resin based on the total solid weight of the coatingcomposition.

The coating composition may comprise from 70 to 97 wt % of thefilm-forming resin based on the total solid weight of the coatingcomposition.

The coating composition may comprise from 70 to 95 wt % of thefilm-forming resin based on the total solid weight of the coatingcomposition.

The coating composition may comprise from 75 to 95 wt % of thefilm-forming resin based on the total solid weight of the coatingcomposition.

The coating composition may comprise from 75 to 92 wt % of thefilm-forming resin based on the total solid weight of the coatingcomposition.

The coating composition may optionally comprise a further crosslinkingmaterial. The further crosslinking agent may be any suitablecrosslinking material. Suitable further crosslinking agents will beknown to a person skilled in the art. Examples of suitable furthercrosslinking materials include, but are not limited to, phenolic resins(or phenol-formaldehyde resins); aminoplast resins (ortriazine-formaldehyde resins); amino resins, such as benzoguanamineresins and/or benzoguanamine-formaldehyde resins; epoxy resins;epoxy-mimic resins, such as those based on bisphenols and otherbisphenol A (BPA) replacements; isocyanate resins; isocyanurate resins,such as triglycidylisocyanurate; hydroxy (alkyl) amide resins, such asβ-hydroxy (alkyl) amide resins; hydroxy(alkyl) urea resins; carbodiimideresins; oxazolines; alkylated carbamate resins; polyacids; anhydrides;organometallic acid-functional materials; polyamines; and/or polyamidesand combinations thereof.

Suitable examples of phenolic resins are those formed from the reactionof a phenol with an aldehyde or a ketone, such as from the reaction of aphenol with an aldehyde, such as from the reaction of a phenol withformaldehyde or acetaldehyde, or even from the reaction of a phenol withformaldehyde. Non-limiting examples of phenols which may be used to formphenolic resins are phenol, butyl phenol, xylenol and cresol. Generalpreparation of phenolic resins is described in “The Chemistry andApplication of Phenolic Resins or Phenoplasts”, Vol V, Part I, edited byDr Oldring; John Wiley and Sons/Cita Technology Limited, London, 1997.The phenolic resins may be of the resol type. By “resol type” we meanresins formed in the presence of a basic (alkaline) catalyst andoptionally an excess of formaldehyde. Suitable examples of commerciallyavailable phenolic resins include, but are not limited to, those soldunder the trade name PHENODUR® commercially available from Allnex, suchas PHENODUR EK-827, PHENODUR VPR1785, PHENODUR PR 515, PHENODUR PR516,PHENODUR PR 517, PHENODUR PR 285, PHENODUR PR612 or PHENODUR PH2024;resins sold under the trade name BAKELITE® commercially available fromSumitomo Bakelite co., ltd., such as BAKELITE 6582 LB, BAKELITE 6535,BAKELITE PF9989 or BAKELITE PF6581; SFC 112 commercially available fromSI Group; DUREZ® 33356 commercially available from SHHPP; ARALINK®40-852 commercially available from Bitrez; or combinations thereof.

Suitable examples of isocyanate resins include, but are not limited to,the following: isophorone diisocyanate (IPDI), such as those sold underthe trade name DESMODUR® commercially available from Cevstro, forexample DESMODUR VP-LS 2078/2 or DESMODUR PL 340 or those sold under thetrade name VESTANAT® commercially available from Evonik, for exampleVESTANANT B 1370, VESTANAT B 118 6A or VESTANAT B 1358 A; blockedaliphatic polyisocyanate based on hexamethylene diisocyanate (HDI), suchas those sold under the trade name DESMODUR® commercially available fromCovestro, for example DESMODUR BL3370 or DESMODUR BL 3175 SN, those soldunder the trade name DURANATE® commercially available from Asahi KASEI,for example DURANATE MF-K60X, those sold under the trade name TOLONATE®commercially available from Vencorex Chemicals, for example TOLONATE D2or those sold under the trade name TRIXENE® commercially available fromBaxenden, for example TRIXENE-BI-7984 or TRIXENE 7981; or combinationsthereof.

The further crosslinking material may be substantially free, may beessentially free or may be completely free of formaldehyde. In thecontext of the further crosslinking material, “substantially free”refers to a further crosslinking material containing less than 5 wt %formaldehyde based on the total solid weight of the crosslinkingmaterial, “essentially free” refers a further crosslinking materialcontaining less than 1 wt % formaldehyde based on the total solid weightof the crosslinking material and “completely free” refers to a furthercrosslinking material containing 0 wt % (i.e. no) formaldehyde based onthe total solid weight of the crosslinking material.

The further crosslinking material may be completely free offormaldehyde.

The coating composition may further comprise water and/or a solvent. Thecoating composition may comprise water and/or a single solvent or amixture of solvents. The coating composition may comprise water, anorganic solvent, a mixture of water and an organic solvent or a mixtureof organic solvents. The coating composition may comprise water and anorganic solvent or water and a mixture of organic solvents.

The organic solvent may have sufficient volatility to essentiallyentirely evaporate from the coating composition during the curingprocess. As a non-limiting example, the curing process may be by heatingat 130-230° C. for 1-15 minutes.

Suitable organic solvents include, but are not limited to, thefollowing: aliphatic hydrocarbons such as mineral spirits and high flashpoint naphtha; aromatic hydrocarbons such as benzene; toluene; xylene;solvent naphtha 100, 150, 200; those available from Exxon-Mobil ChemicalCompany under the SOLVESSO® trade name; alcohols such as ethanol;n-propanol; isopropanol; n-butanol; pentanol; amyl alcohol;1-methoxy-2-propanol; and butoxy ethanol; ketones such as acetone;cyclohexanone; methylisobutyl ketone; methyl ethyl ketone; esters suchas ethyl acetate; butyl acetate; n-hexyl acetate; RHODIASOLV® RPDE (ablend of succinic and adipic esters commercially available from Rhodia);glycols such as butyl glycol; glycol ethers such as methoxypropanol;ethylene glycol monomethyl ether; ethylene glycol monobutyl ether; thoseavailable from Dow under the DOWANOL® trade name, such as DOWANOL PM,DOWANOL DPM and DOWANOL PPH, for example; and combinations thereof.

The coating composition may comprise any suitable amount of water and/orsolvent. The coating composition may comprise from 1 to 90 wt %, such asfrom 5 to 95 wt %, such as from 10 to 90 wt %, such as from 20 to 80 wt%, such as from 30 to 75 wt %, such as from 40 to 75 wt %, such as from50 to 75 wt % or even from 40 to 75 wt % water and/or solvent based onthe total weight of the coating composition.

The coating composition may comprise any suitable amount of solvent. Thecoating composition may comprise from 1 to 50 wt %, such as from 2 to 40wt %, such as from 5 to 30 wt %, such as from 5 to 20 wt %, such as from5 to 15 wt %, or even 10 wt % solvent based on the total weight of thecoating composition.

The crosslinking material and/or film-forming resin may be dissolved ordispersed in the said solvent during and/or after its formation.

The coating composition may further comprise a catalyst. Suitablecatalysts will be well known to the person skilled in the art. Thecatalyst may be a non-metal, a metal catalyst or a combination thereof.Suitable non-metal catalysts include, but are not limited to, thefollowing: phosphoric acid; blocked phosphoric acid; phosphatised resinssuch as, for example, phosphatised epoxy resins and phosphatised acrylicresins; CYCAT® XK 406 N (commercially available from Allnex); sulfuricacid; sulfonic acid; CYCAT 600 (commercially available from Allnex);NACURE® 5076 or NACURE 5925 (commercially available from Kingindustries); acid phosphate catalyst such as NACURE XC 235 (commerciallyavailable from King Industries); and combinations thereof. Suitablemetal catalysts will be well known to the person skilled in the art.Suitable metal catalysts include, but are not limited to, the following:tin containing catalysts, such as monobutyl tin tris (2-ethylhexanoate);zirconium containing catalysts, such as KKAT® 4205 (commerciallyavailable from King Industries); titanate based catalysts, such astetrabutyl titanate TnBT (commercially available from Sigma Aldrich);zinc based catalysts such as zinc octoate; tertiary amines such asdimethyldodecylamine; onium salts such as ammonium and phosphoniumsalts; and combinations thereof.

The catalyst, when present, may be used in the coating composition inany suitable amount. The coating composition may comprise from 0.001 to10 wt %, such as from 0.001 to 5 wt %, such as from 0.01 to 5 wt %, suchas from 0.05 to 3 wt %, such as from 0.1 to 2 wt %, such as from 0.1 to1 wt %, or even from 0.1 to 0.5 wt % of the catalyst, when present,based on the total solid weight of the coating composition.

The coating composition may comprise other optional materials well knownin the art of formulating coatings, such as colorants, plasticizers,abrasion-resistant particles, anti-oxidants, hindered amine lightstabilizers, UV light absorbers and stabilizers, surfactants, flowcontrol agents, thixotropic agents, fillers, organic co-solvents,reactive diluents, catalysts, grind vehicles, lubricants, waxes andother customary auxiliaries.

As used herein, the term “colorant” means any substance that impartscolor and/or other opacity and/or other visual effect to thecomposition. The colorant can be added to the coating in any suitableform, such as discrete particles, dispersions, solutions and/or flakes.A single colorant or a mixture of two or more colorants can be used inthe coatings of the present invention. Suitable colorants are listed inU.S. Pat. No. 8,614,286, column 7, line 2 through column 8, line 65,which is incorporated by reference herein. Particularly suitable forpackaging coatings are those approved for food contact, such as titaniumdioxide; iron oxides, such as black iron oxide; aluminum paste; aluminumpowder such as aluminum flake; carbon black; ultramarine blue;phthalocyanines, such as phthalocyanine blue and phthalocyanine green;chromium oxides, such as chromium green oxide; graphite fibrils; ferriedyellow; quindo red; and combinations thereof, and those listed inArticle 178.3297 of the Code of Federal Regulations, which isincorporated by reference herein.

The colorant, when present, may be used in the coating composition inany suitable amount. The coating composition may comprise up to 90 wt %,such as up to 50 wt %, or even up to 10 wt % colorant, when present,based on the total solid weight of the coating composition.

Suitable lubricants will be well known to the person skilled in the art.Suitable examples of lubricants include, but are not limited to, thefollowing: carnauba wax and polyethylene type lubricants. The coatingcomposition may comprise at least 0.01 wt % lubricant, when present,based on the total solid weight of the coating composition.

Surfactants may optionally be added to the coating composition in orderto aid in flow and wetting of the substrate. Suitable surfactants willbe well known to the person skilled in the art. The surfactant, whenpresent, may be chosen to be compatible with food and/or beveragecontainer applications. Suitable surfactants include, but are notlimited to, the following: alkyl sulphates (e.g., sodium laurylsulphate); ether sulphates; phosphate esters; sulphonates; and theirvarious alkali, ammonium, amine salts; aliphatic alcohol ethoxylates;alkyl phenol ethoxylates (e.g. nonyl phenol polyether); salts and/orcombinations thereof. The coating composition may comprise from 0.01 wt% to 10 wt %, such as from 0.01 to 5 wt %, or even from 0.01 to 2 wt %surfactant, when present, based on the total solid weight of the coatingcomposition.

The coating compositions of the present invention may be substantiallyfree, may be essentially free or may be completely free of bisphenol A(BPA) and derivatives thereof. Derivatives of bisphenol A include, forexample, bisphenol A diglycidyl ether (BADGE). The coating compositionsof the present invention may also be substantially free, may beessentially free or may be completely free of bisphenol F (BPF) andderivatives thereof. Derivatives of bisphenol F include, for example,bisphenol F diglycidyl ether (BPFG). The compounds or derivativesthereof mentioned above may not be added to the compositionintentionally but may be present in trace amounts because of unavoidablecontamination from the environment. “Substantially free” refers tocoating compositions, or components thereof, containing less than 1000parts per million (ppm) of any of the compounds or derivatives thereofmentioned above. “Essentially free” refers to coating compositions, orcomponents thereof, containing less than 100 ppm of any of the compoundsor derivatives thereof mentioned above. By “Completely free” refers tocoating compositions, or components thereof, containing less than 20parts per billion (ppb) of any of the compounds or derivatives thereofmentioned above.

The coating compositions of the present invention may be substantiallyfree, may be essentially free or may be completely free of dialkyltincompounds, including oxides or other derivatives thereof. Examples ofdialkyltin compounds include, but are not limited to, the following:dibutyltindilaurate (DBTDL); dioctyltindilaurate; dimethyltin oxide;diethyltin oxide; dipropyltin oxide; dibutyltin oxide (DBTO);dioctyltinoxide (DOTO) or combinations thereof. By “substantially free”we mean to refer to coating compositions containing less than 1000 partsper million (ppm) of any of the compounds or derivatives thereofmentioned above. By “essentially free” we mean to refer to coatingcompositions containing less than 100 ppm of any of the compounds orderivatives thereof mentioned above. By “completely free” we mean torefer to coating compositions containing less than 20 parts per billion(ppb) of any of the compounds or derivatives thereof.

The coating compositions may be substantially free, may be essentiallyfree or may be completely free of formaldehyde. “Substantially free”refers to coating compositions, or components thereof, containing lessthan 1000 parts per million (ppm) of formaldehyde. “Essentially free”refers to coating compositions, or components thereof, containing lessthan 100 ppm of any of formaldehyde. “Completely free” refers to coatingcompositions, or components thereof, containing less than 20 parts perbillion (ppb) of formaldehyde.

The coating compositions may be applied to any suitable substrate. Thesubstrate may be formed of metal, plastic, composite and/or wood. Thesubstrate may be a metal substrate.

The substrate may be an article such as an automotive product, ahousehold or office appliance, furniture item or tool, a poweredindustrial product, a consumer electronics article, an architecturalproduct or a product protected by an intumescent coating.

Examples of suitable metal substrates include, but are not limited to,food and/or beverage packaging, components used to fabricate suchpackaging or monobloc aerosol cans and/or tubes.

The food and/or beverage packaging may be a can, such as a metal can.Examples of cans include, but are not limited to, two-piece cans,three-piece cans and the like. Suitable examples of monobloc aerosolcans and/or tubes include, but are not limited to, deodorant and hairspray containers. Monobloc aerosol cans and/or tubes may be aluminiummonobloc aerosol cans and/or tubes.

The substrate may be a food and/or beverage packaging or component usedto fabricate such packaging.

The food and/or beverage can may comprise a can body and a can end.

The substrate may be a monobloc aerosol can and/or tube.

The application of various pre-treatments and coatings to packaging iswell established. Such treatments and/or coatings, for example, can beused in the case of metal cans, wherein the treatment and/or coating isused to retard or inhibit corrosion, provide a decorative coating,provide ease of handling during the manufacturing process, and the like.Coatings can be applied to the interior of such cans to prevent thecontents from contacting the metal of the container. Contact between themetal and a food or beverage, for example, can lead to corrosion of ametal container, which can then contaminate the food or beverage. Thisis particularly true when the contents of the can are acidic in nature.The coatings applied to the interior of metal cans also help preventcorrosion in the headspace of the cans, which is the area between thefill line of the product and the can lid; corrosion in the headspace isparticularly problematic with food products having a high salt content.Coatings can also be applied to the exterior of metal cans.

The coating compositions are particularly applicable for use with coiledmetal stock, such as the coiled metal stock from which the ends of cansare made (“can end stock”), and end caps and closures are made(“cap/closure stock”). Since coatings designed for use on can end stockand cap/closure stock may be applied prior to the piece being cut andstamped out of the coiled metal stock, they may be flexible andextensible. For example, such stock may be coated on both sides.Thereafter, the coated metal stock is punched. For can ends, the metalis then scored for the “pop-top” opening and the pop-top ring is thenattached with a pin that is separately fabricated. The end is thenattached to the can body by an edge rolling process. A similar procedureis done for “easy open” can ends. For easy open can ends, a scoresubstantially around the perimeter of the lid allows for easy opening orremoving of the lid from the can, such as by means of a pull tab. Forcaps and closures, the cap/closure stock may be coated, such as by rollcoating, and the cap or closure stamped out of the stock; it ispossible, however, to coat the cap/closure after formation. Coatings forcans subjected to relatively stringent temperature and/or pressurerequirements should also be resistant to popping, corrosion, blushingand/or blistering.

The substrate may be a can end, such as a metal can end.

The substrate may be a package coated at least in part with any of thecoating compositions described herein. A “package” is anything used tocontain another item, particularly for shipping from a point ofmanufacture to a consumer, and for subsequent storage by a consumer. Apackage will be therefore understood as something that is sealed so asto keep its contents free from deterioration until opened by a consumer.The manufacturer will often identify the length of time during which thefood or beverage will be free from spoilage, which may range fromseveral months to years. Thus, the present “package” is distinguishedfrom a storage container or bakeware in which a consumer might makeand/or store food; such a container would only maintain the freshness orintegrity of the food item for a relatively short period of time. Apackage according to the present invention can be made of metal ornon-metal, for example, plastic or laminate, and be in any form. Anexample of a suitable package is a laminate tube. Another example of asuitable package is metal can. The term “metal can” includes any type ofmetal can, container or any type of receptacle or portion thereof thatis sealed by the food and/or beverage manufacturer to minimize oreliminate spoilage of the contents until such package is opened by theconsumer. One example of a metal can is a food can; the term “foodcan(s)” is used herein to refer to cans, containers or any type ofreceptacle or portion thereof used to hold any type of food and/orbeverage. The term “metal can(s)” specifically includes food cans andalso specifically includes “can ends” including “E-Z open ends”, whichmay be stamped from can end stock and used in conjunction with thepackaging of food and beverages. The term “metal cans” also specificallyincludes metal caps and/or closures such as bottle caps, screw top capsand lids of any size, lug caps, and the like. The metal cans can be usedto hold other items as well, including, but not limited to, personalcare products, bug spray, spray paint, and any other compound suitablefor packaging in an aerosol can. The cans can include “two piece cans”and “three-piece cans” as well as drawn and ironed one-piece cans; suchone piece cans often find application with aerosol products. Packagescoated according to the present invention can also include plasticbottles, plastic tubes, laminates and flexible packaging, such as thosemade from PE, PP, PET and the like. Such packaging could hold, forexample, food, toothpaste, personal care products and the like.

The coating compositions can be applied to the interior and/or theexterior of the package. The coating compositions could also be appliedas a rim coat to the bottom of the can. The rim coat functions to reducefriction for improved handling during the continued fabrication and/orprocessing of the can. The coating compositions can also be applied tocaps and/or closures; such application can include, for example, aprotective varnish that is applied before and/or after formation of thecap/closure and/or a pigmented enamel post applied to the cap,particularly those having a scored seam at the bottom of the cap.Decorated can stock can also be partially coated externally with thecoating described herein, and the decorated, coated can stock used toform various metal cans.

Metal coils, having wide application in many industries, are alsosubstrates that can be coated according to the present invention. Coilcoatings also may comprise a colorant.

The coating compositions may be applied to at least a portion of thesubstrate. For example, when the coating compositions are applied to afood and/or beverage can, the coating compositions may be applied to atleast a portion of an internal and/or external surface of said foodand/or beverage can. For example, when the coating compositions areapplied to a food and/or beverage can, the coating compositions may beapplied to at least a portion of an internal surface of said food and/orbeverage can.

The coating composition may be applied as a repair coating for componentparts of food and beverage cans. For example, as a repair coating for afull aperture easy open end for food cans. This end component may berepair coated, after fabrication, by airless spraying of the material onto the exterior of the score line. Other uses as repair coatings includethe coating of seams and welds, such as side seams for which the coatingmay be applied to the area by spraying (airless or air driven) or rollercoating. Repair coating can also include protection of vulnerable areaswhere corrosion may be likely due to damage, these areas includeflanges, rims and bottom rims where the coating may be applied byspraying, roller coating flow or dip coating.

An automotive product may be a vehicle or any part thereof. Any part orany surface of the vehicle which may undergo coating to improve aproperty thereof (for example its luster, scratch resistance, corrosionresistance or UV resistance) may be a coating with a composition asdefined herein.

The term “vehicle” is used in its broadest sense and includes (withoutlimitation) all types of aircraft, spacecraft, watercraft, and groundvehicles. For example, a vehicle can include, aircraft such as airplanesincluding private aircraft, and small, medium, or large commercialpassenger, freight, and military aircraft; helicopters, includingprivate, commercial, and military helicopters; aerospace vehiclesincluding, rockets and other spacecraft. Vehicles can include groundvehicles such as, for example, trailers, cars, trucks, buses, coaches,vans, ambulances, fire engines, motorhomes, caravans, go-karts, buggies,fork-lift trucks, sit-on lawnmowers, agricultural vehicles such as, forexample, tractors and harvesters, construction vehicles such as, forexample, diggers, bulldozers and cranes, golf carts, motorcycles,bicycles, trains, and railroad cars. Vehicles can also includewatercraft such as, for example, ships, submarines, boats, jet-skis andhovercraft.

Parts of vehicles coated may include vehicular body parts (e.g., withoutlimitation, doors, body panels, trunk deck lids, roof panels, hoods,roofs and/or stringers, rivets, wheels, landing gear components, and/orskins used on an aircraft), hulls, marine superstructures, vehicularframes, chassis, and vehicular parts not normally visible in use, suchas engine parts, motorcycle fairings and fuel tanks, fuel tank surfacesand other vehicular surfaces exposed to or potentially exposed to fuels,aerospace solvents and aerospace hydraulic fluids. Any vehicular partswhich may benefit from coating as defined herein may undergo coating,whether exposed to or hidden from view in normal use.

Household and office appliances, furniture items and tools as definedherein are appliances, furniture items and tools used in the home,including the garden, or in office environments. They may include fabricwashers, dishwashers, dryers, refrigerators, stoves, microwave ovens,computer equipment and printers, air conditioning units, heat pumpunits, lawn and garden equipment including lawn furniture, hot tubs,lawnmowers, garden tools, hedge trimmers, string trimmers (strimmers),chainsaws, garden waster shedders, garden hand tools such as, forexample, spades, forks, rakes and cutting tools, cupboards, desks,table, chairs, cabinets and other articles. Any parts of any sucharticles which may benefit from coating as defined herein may undergocoating; for example panels of appliances or furniture and handles oftools.

A powered industrial product may include, for example, pumps,electricity generators, air compressors, industrial heat pumps and airconditioners, batteries and cement mixers. Any parts which benefit fromcoating as defined herein may undergo coating; for example panels andcasings.

A consumer electronics article may be, for example, a computer, computercasing, television, cellphone, pager, camera, calculator, printer,scanner, digital decoder, clock, audio player, headphones or tablet.

An architectural product may be, for example, a door, window, doorframe, window frame, beam or support, or a panel, walling item orroofing item used in building construction, or a solar panel, a windturbine, an oil/gas well, an off-shore rig, a storage tank, or intransportation infrastructure or utilities infrastructure.

Products protected by intumescent coatings may be metallic structures,for example steel structures, which are coating with an intumescentcoating. The metallic structures may be load bearing parts of buildings.Unprotected steel may begin to soften at around 425° C. and loseapproximately half of its strength by 650° C. Intumescent coatings areemployed to retard the temperature increase of the steel, or othersubstrate. An intumescent coating may be improved by incorporation ofthe defined acrylic polyester resin into the matrix of the intumescentmaterial prior to its coating onto a metallic substrate to be protected.The acrylic polyester resin may be present in an amount of at least 1 wt%, such as at least 2 wt %, for example at least 4 wt %, or at least 5%.The acrylic polyester resin may be present in an amount of up to 50 wt %by weight, such as up to 30 wt %, for example up to 25 wt %. Thesedefinitions refer to the weight of the acrylic polyester resin by weightof the admixed acrylic polyester resin/intumescent matrix material to beapplied to a substrate.

Articles coated may fall in two or more of the categories set out above.For example computer equipment may be regarded as a household or as anoffice item, and as a consumer electronics item. A beam or support—anarchitectural item—may be coated with an intumescent material.

In the uses defined above a coating composition may be to coat surfacesand parts thereof (except for the use in an intumescent coating which isan admixture). A part may include multiple surfaces. A part may includea portion of a larger part, assembly, or apparatus. A portion of a partmay be coated with an aqueous composition or powder composition asdefined herein or the entire part may be coated.

The substrate may be new (i.e., newly constructed or fabricated) or itmay be refurbished, such as, for example, in the case of refinishing orrepairing a component of an automobile or aircraft.

As mentioned above, the substrate coated may comprise a vehicle. Forexample, an aqueous or powder composition may be utilized in coating aF/A-18 jet or related aircraft such as the F/A-18E Super Hornet andF/A-18F (produced by McDonnell Douglas/Boeing and Northrop); in coatingthe Boeing 787 Dreamliner, 737, 747, 717 passenger jet aircraft, andrelated aircraft (produced by Boeing Commercial Airplanes); in coatingthe V-22 Osprey; VH-92, S-92, and related aircraft (produced by NAVAIRand Sikorsky); in coating the G650, G600, G550, G500, G450, and relatedaircraft (produced by Gulfstream); and in coating the A350, A320, A330,and related aircraft (produced by Airbus). An aqueous or powdercomposition may be used as a coating for use in any suitable commercial,military, or general aviation aircraft such as, for example, thoseproduced by Bombardier Inc. and/or Bombardier Aerospace such as theCanadair Regional Jet (CRJ) and related aircraft; produced by LockheedMartin such as the F-22 Raptor, the F-35 Lightning, and relatedaircraft; produced by Northrop Grumman such as the B-2 Spirit andrelated aircraft; produced by Pilatus Aircraft Ltd.; produced by EclipseAviation Corporation; or produced by Eclipse Aerospace (KestrelAircraft).

The coating compositions may be applied to the substrate by any suitablemethod. Suitable methods of applying the coating compositions will bewell known to a person skilled in the art. Suitable application methodsfor the coating compositions include, but are not limited to, thefollowing: electrocoating, such as electrodeposition; spraying;electrostatic spraying; dipping; rolling; brushing; and the like.

The coating compositions may be applied to the substrate, or a portionthereof, as a single layer or as part of a multi-layer system. Thecoating compositions may be applied as a single layer. The coatingcompositions may be applied to an uncoated substrate. For the avoidanceof doubt, an uncoated substrate extends to a surface that is cleanedprior to application. The coating compositions may be applied on top ofanother paint layer as part of a multi-layer system. For example, thecoating compositions may be applied on top of a primer. The coatingcompositions may form an intermediate layer or a top coat layer. Thecoating compositions may be applied as the first coat of a multi coatsystem. The coating compositions may be applied as an undercoat or aprimer. The second, third, fourth etc. coats may comprise any suitablepaint such as those containing, for example, epoxy resins; polyesterresins; polyurethane resins; polysiloxane resins; hydrocarbon resins orcombinations thereof. The second, third, fourth etc. coats may comprisepolyester resins. The second, third, fourth etc. coats may be a liquidcoating or a powder coating.

It will be appreciated by a person skilled in the art that the coatingcompositions may be applied before or after forming the article, such asthe packaging. For example, the coating compositions may be applied tometal substrate which is then shaped and formed into a metal article, orthe coating composition may be applied to the preformed article.

The coating compositions may be applied to a substrate once or multipletimes.

The coating compositions may be applied to the substrate by any suitablemethod. Methods of applying the coating compositions will be well knownto a person skilled in the art. Suitable application methods for thecoating compositions include, but are not limited to, the following:electrocoating; spraying; electrostatic spraying; dipping; rolling;brushing; and the like.

Further information about suitable application methods of applyingsuitable coating compositions to substrates will now be given.

A liquid coating composition may be electrophoretically deposited uponany electrically conductive substrate. Suitable substrates include metalsubstrates, metal alloy substrates, and/or substrates that have beenmetallized, such as nickel-plated plastic. Additionally, substrates maycomprise non-metal conductive materials including composite materialssuch as, for example, materials comprising carbon fibers or conductivecarbon. The metal or metal alloy may comprise, for example, cold rolledsteel, hot rolled steel, steel coated with zinc metal, zinc compounds,or zinc alloys, such as electrogalvanized steel, hot-dipped galvanizedsteel, galvannealed steel, nickel-plated steel, and steel plated withzinc alloy. The substrate may comprise an aluminum alloy. Non-limitingexamples of aluminum alloys include the 1XXX, 2XXX, 3XXX, 4XXX, 5XXX,6XXX, or 7XXX series as well as clad aluminum alloys and cast aluminumalloys, such as, for example, the A356 series. The substrate maycomprise a magnesium alloy. Non-limiting examples of magnesium alloys ofthe AZ31B, AZ91C, AM60B, or EV31A series also may be used as thesubstrate. The substrate may also comprise other suitable non-ferrousmetals such as titanium or copper, as well as alloys of these materials.

The part to be coated may be in the shape of a cylinder, such as a pipe,including, for example, a cast iron or steel pipe. The metal substratealso may be in the form of, for example, a sheet of metal or afabricated part. The substrate may also comprise conductive ornon-conductive substrates at least partially coated with a conductivecoating. The conductive coating may comprise a conductive agent such as,for example, graphene, conductive carbon black, conductive polymers, orconductive additives. It will also be understood that the substrate maybe pretreated with a pretreatment solution. Non-limiting examples of apretreatment solution include a zinc phosphate pretreatment solutionsuch as, for example, those described in U.S. Pat. Nos. 4,793,867 and5,588,989, a zirconium containing pretreatment solution such as, forexample, those described in U.S. Pat. Nos. 7,749,368 and 8,673,091.Other non-limiting examples of a pretreatment solution include thosecomprising trivalent chromium, hexavalent chromium, lithium salts,permanganate, rare earth metals, such as yttrium, or lanthanides, suchas cerium. Another non-limiting example of a suitable surfacepretreatment solution is a sol-gel, such as those comprisingalkoxy-silanes, alkoxy-zirconates, and/or alkoxy-titanates.Alternatively, the substrate may be a non-pretreated substrate, such asa bare substrate, that is not pretreated by a pretreatment solution.

The substrate may optionally be subjected to other treatments prior tocoating. For example, the substrate may be cleaned, cleaned anddeoxidized, anodized, acid pickled, plasma treated, laser treated, orion vapor deposition (IVD) treated. These optional treatments may beused on their own or in combination with a pretreatment solution.

A liquid composition may be utilized in an electrocoating layer that ispart of a multi-layer coating composite comprising a substrate withvarious coating layers. The coating layers may optionally include apretreatment layer, such as a phosphate layer (e.g., zinc phosphatelayer) or metal oxide layer (e.g., zirconium oxide layer), anelectrocoating layer which results from an aqueous composition,optionally primer layer(s) and suitable topcoat layer(s) (e.g., basecoat, clear coat layer, pigmented monocoat, and color-plus-clearcomposite compositions). It is understood that suitable additionalcoating layers include any of those known in the art, and eachindependently may be waterborne, solvent-borne, in solid particulateform (i.e., a powder coating composition), or in the form of a powderslurry. The additional coating compositions may comprise a film-formingpolymer, crosslinking material and, if a colored base coat or monocoat,pigment. The primer layer(s) may optionally be disposed between theelectrocoating layer and the topcoat layer(s). Alternatively, thetopcoat layer(s) may be omitted such that the composite comprises theelectrocoating layer and primer layer(s).

Moreover, the topcoat layer(s) may be applied directly onto theelectrodepositable coating layer. In other words, the substrate may lacka primer layer such that the composite comprises the electrocoatinglayer and topcoat layer(s). For example, a basecoat layer may be applieddirectly onto at least a portion of the electrodepositable coatinglayer.

It will also be understood that any of the topcoat layers may be appliedonto an underlying layer, despite the fact that the underlying layer hasnot been fully cured. For example, a clearcoat layer may be applied ontoa basecoat layer even though the basecoat layer has not been subjectedto a curing step (wet-on-wet). Both layers may then be cured during asubsequent curing step thereby eliminating the need to cure the basecoatlayer and the clearcoat layer separately.

“Powder” and like terms, as used herein, refers to materials that are inthe form of solid particulates, as opposed to materials which are in theliquid form.

Powder coating compositions may be applied by any suitable method.Methods of applying said powder coating compositions will be well knownto a person skilled in the art. Suitable application methods include,such as electrodeposition, or applied by ultra corona discharge forexample. The powder coating compositions may be applied by ultra coronadischarge.

When the substrate is electrically conductive, the powder coatingcomposition may be electrostatically applied. Electrodepositiongenerally involves drawing the coating composition from a fluidized bedand propelling it through a corona field. The particles of the coatingcomposition become charged as they pass through the corona field and areattracted to and deposited upon the electrically conductive substrate,which is grounded. As the charged particles begin to build up, thesubstrate becomes insulated, thus limiting further particle deposition.

The coating compositions may be in the form of a liquid or a powder.

The coating compositions may be in the form of a liquid. The coatingcompositions may be solvent-borne or aqueous.

The coating compositions may be applied to the substrate by spraying.Thus, the coating compositions may be spray compositions. For theavoidance of doubt, by the term ‘spray composition’ and like terms asused herein is meant, unless specified otherwise, that the coating issuitable to be applied to a substrate by spraying, i.e. is sprayable.

The coating compositions may be applied to any suitable dry filmthickness. The coating compositions may be applied to a dry filmthickness from 1 to 100 microns (μm), such as from 1 to 75 μm, such asfrom 1 to 50 μm, such as from 1 to 40 μm, such as from 1 to 20 μm, oreven from 1 to 10 μm.

The coating compositions and/or layers deposited from the same, as wellas any pretreatment layer, primer layer or topcoat layer, may besubstantially free of chromium or chromium-containing compounds meaningthat chromium or chromium-containing compounds are not intentionallyadded, but may be present in trace amounts, such as because ofimpurities or unavoidable contamination from the environment. In otherwords, the amount of material is so small that it does not affect theproperties of the composition; this may further include that chromium orchromium-containing compounds are not present in an aqueous or powdercomposition and/or layers deposited from the same, as well as anypretreatment layer, primer layer or topcoat layer, in such a level thatthey cause a burden on the environment. The term “substantially free”means that a coating composition and/or layers deposited from the same,as well as any pretreatment layer, primer layer or topcoat layer,contain less than 10 ppm of chromium, based on total solids weight ofthe composition, the layer, or the layers, respectively, if any at all.The term “essentially free” means that a coating composition and/orlayers deposited from the same, as well as any pretreatment layer,primer layer or topcoat layer, contain less than 1 ppm of chromium,based on total solids weight of the composition or the layer, or layers,respectively, if any at all. The term “completely free” means that acoating composition and/or layers comprising the same, as well as anypretreatment layer, primer layer or topcoat layer, contain less than 1ppb of chromium, based on total solids weight of the composition, thelayer, or the layers, respectively, if any at all.

The coating compositions may be cured by any suitable method. Thecoating composition may be cured by heat curing, radiation curing or bychemical curing, such as by heat curing.

The coating composition, when heat cured, may be cured at any suitabletemperature. The coating composition, when heat cured, may be cured to apeak metal temperature (PMT) of 100° C. to 350° C., such as 150° C. to350° C., such as from 175° C. to 320° C., such as from 190° C. to 300°C., or even from 200° C. to 280° C. For the avoidance of doubt, the term“peak metal temperature”, and like terms as used herein, is meant unlessspecified otherwise the maximum temperature reached by the metalsubstrate during exposure to a heat during the heat curing process. Inother words, the peak metal temperature (PMT) is the maximum temperaturereached by the metal substrate and not the temperature which is appliedthereto. It will be appreciated by a person skilled in the art that thetemperature reached by the metal substrate may be lower than thetemperature which is applied thereto or may be substantially equal tothe temperature which is applied thereto. The temperature reached by themetal substrate may be lower than the temperature which is appliedthereto.

Curing the coating compositions may form a cured film.

The ester, amide and/or thioester of the cyclic unsaturated acidanhydride and/or diacid derivative thereof may form an acid anhydridegroup at an elevated temperature, such as above 100° C., for exampleduring curing, by removal of an alcohol, amine and/or thiol. The acidanhydride group formed may then be reacted with a hydroxyl group to forma carboxyl group.

The diacid derivative of the cyclic unsaturated acid anhydride may forman acid anhydride group at an elevated temperature, such as above 100°C., for example during curing, by removal of water. The acid anhydridegroup formed may then be reacted with a hydroxyl group to form acarboxyl group.

The term “alk” or “alkyl”, as used herein unless otherwise defined,relates to saturated hydrocarbon radicals being straight, branched,cyclic or polycyclic moieties or combinations thereof and contain 1 to20 carbon atoms, such as 1 to 10 carbon atoms, such as 1 to 8 carbonatoms, such as 1 to 6 carbon atoms, or even 1 to 4 carbon atoms. Theseradicals may be optionally substituted with a chloro, bromo, iodo,cyano, nitro, OR¹⁹, OC(O)R²⁰, C(O)R²¹, C(O)OR²², NR²³R²⁴, C(O)NR²⁵R²⁶,SR²⁷, C(O)SR²⁷, C(S)NR²⁵R²⁶, aryl or Het, wherein R¹⁹ to R²⁷ eachindependently represent hydrogen, aryl or alkyl, and/or be interruptedby oxygen or sulphur atoms, or by silano or dialkylsiloxane groups.Examples of such radicals may be independently selected from methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,2-methylbutyl, pentyl, iso-amyl, hexyl, cyclohexyl, 3-methylpentyl,octyl and the like. The term “alkylene”, as used herein, relates to abivalent radical alkyl group as defined above. For example, an alkylgroup such as methyl which would be represented as —CH₃, becomesmethylene, —CH₂—, when represented as an alkylene. Other alkylene groupsshould be understood accordingly.

The term “alkenyl”, as used herein, relates to hydrocarbon radicalshaving, such as up to 4, double bonds, being straight, branched, cyclicor polycyclic moieties or combinations thereof and containing from 2 to18 carbon atoms, such as 2 to 10 carbon atoms, such as from 2 to 8carbon atoms, such as 2 to 6 carbon atoms, or even 2 to 4 carbon atoms.These radicals may be optionally substituted with a hydroxyl, chloro,bromo, iodo, cyano, nitro, OR¹⁹, OC(O)R²⁰, C(O)R²¹, C(O)OR²², NR²³R²⁴,C(O)NR²⁵R²⁶, SR²⁷, C(O)SR²⁷, C(S)NR²⁵R²⁶, or aryl, wherein R¹⁹ to R²⁷each independently represent hydrogen, aryl or alkyl, and/or beinterrupted by oxygen or sulphur atoms, or by silano or dialkylsiloxanegroups. Examples of such radicals may be independently selected fromalkenyl groups include vinyl, allyl, isopropenyl, pentenyl, hexenyl,heptenyl, cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl,1-propenyl, 2-butenyl, 2-methyl-2-butenyl, isoprenyl, farnesyl, geranyl,geranylgeranyl and the like. The term “alkenylene”, as used herein,relates to a bivalent radical alkenyl group as defined above. Forexample, an alkenyl group such as ethenyl which would be represented as—CH═CH2, becomes ethenylene, —CH═CH—, when represented as an alkenylene.Other alkenylene groups should be understood accordingly.

The term “alkynyl”, as used herein, relates to hydrocarbon radicalshaving, such as up to 4, triple bonds, being straight, branched, cyclicor polycyclic moieties or combinations thereof and having from 2 to 18carbon atoms, such as 2 to 10 carbon atoms, such as from 2 to 8 carbonatoms, such as from 2 to 6 carbon atoms, or even from 2 to 4 carbonatoms. These radicals may be optionally substituted with a hydroxy,chloro, bromo, iodo, cyano, nitro, OR¹⁹, OC(O)R²⁰, C(O)R²¹, C(O)OR²²,NR²³R²⁴, C(O)NR²⁵R²⁶, SR²⁷, C(O)SR²⁷, C(S)NR²⁵R²⁶, or aryl, wherein R¹⁹to R²⁷ each independently represent hydrogen, aryl or lower alkyl,and/or be interrupted by oxygen or sulphur atoms, or by silano ordialkylsiloxane groups. Examples of such radicals may be independentlyselected from alkynyl radicals include ethynyl, propynyl, propargyl,butynyl, pentynyl, hexynyl and the like. The term “alkynylene”, as usedherein, relates to a bivalent radical alkynyl group as defined above.For example, an alkynyl group such as ethynyl which would be representedas —C≡CH, becomes ethynylene, —C≡C—, when represented as an alkynylene.Other alkynylene groups should be understood accordingly.

The term “aryl” as used herein, relates to an organic radical derivedfrom an aromatic hydrocarbon by removal of one hydrogen, and includesany monocyclic, bicyclic or polycyclic carbon ring of up to 7 members ineach ring, wherein a ring is aromatic. These radicals may be optionallysubstituted with a hydroxy, chloro, bromo, iodo, cyano, nitro, OR¹⁹,OC(O)R²⁰, C(O)R²¹, C(O)OR²², NR²³R²⁴, C(O)NR²⁵R²⁶, SR²⁷, C(O)SR²⁷,C(S)NR²⁵R²⁶, or aryl, wherein R¹⁹ to R²⁷ each independently representhydrogen, aryl or lower alkyl, and/or be interrupted by oxygen orsulphur atoms, or by silano or dialkylsilcon groups. Examples of suchradicals may be independently selected from phenyl, p-tolyl,4-methoxyphenyl, 4-(tert-butoxy)phenyl, 3-methyl-4-methoxyphenyl,4-fluorophenyl, 4-chlorophenyl, 3-nitrophenyl, 3-aminophenyl,3-acetamidophenyl, 4-acetamidophenyl, 2-methyl-3-acetamidophenyl,2-methyl-3-aminophenyl, 3-methyl-4-aminophenyl, 2-amino-3-methylphenyl,2,4-dimethyl-3-aminophenyl, 4-hydroxyphenyl, 3-methyl-4-hydroxyphenyl,1-naphthyl, 2-naphthyl, 3-amino-1-naphthyl, 2-methyl-3-amino-1-naphthyl,6-amino-2-naphthyl, 4,6-dimethoxy-2-naphthyl, tetrahydronaphthyl,indanyl, biphenyl, phenanthryl, anthryl or acenaphthyl and the like. Theterm “arylene”, as used herein, relates to a bivalent radical aryl groupas defined above. For example, an aryl group such as phenyl which wouldbe represented as -Ph, becomes phenylene, -Ph-, when represented as anarylene. Other arylene groups should be understood accordingly.

For the avoidance of doubt, the reference to alkyl, alkenyl, alkynyl,aryl or aralkyl in composite groups herein should be interpretedaccordingly, for example the reference to alkyl in aminoalkyl or alk inalkoxyl should be interpreted as alk or alkyl above etc.

As used herein, unless otherwise expressly specified, all numbers suchas those expressing values, ranges, amounts or percentages may be readas if prefaced by the word “about”, even if the term does not expresslyappear. Also, the recitation of numerical ranges by endpoints includesall integer numbers and, where appropriate, fractions subsumed withinthat range (e.g. 1 to 5 can include 1, 2, 3, 4 when referring to, forexample, a number of elements, and can also include 1.5, 2, 2.75 and3.80, when referring to, for example, measurements). The recitation ofend points also includes the end point values themselves (e.g. from 1.0to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein isintended to include all sub-ranges subsumed therein.

Singular encompasses plural and vice versa. For example, althoughreference is made herein to “a” crosslinking material, “a” film-formingbinder, “an” anhydride, and the like, one or more of each of these andany other components can be used. As used herein, the term “polymer”refers to oligomers and both homopolymers and copolymers, and the prefix“poly” refers to two or more. Including, for example and like termsmeans including for example but not limited to.

The terms “comprising”, “comprises” and “comprised of” as used hereinare synonymous with “including”, “includes” or “containing”, “contains”,and are inclusive or open-ended and do not exclude additional,non-recited members, elements or method steps. Additionally, althoughthe present invention has been described in terms of “comprising”, thecoating compositions detailed herein may also be described as“consisting essentially of” or “consisting of”.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itselfor any combination of two or more of the listed items can be employed.For example, if a list is described as comprising group A, B, and/or C,the list can comprise A alone; B alone; C alone; A and B in combination;A and C in combination, B and C in combination; or A, B, and C incombination.

All of the features contained herein may be combined with any of theabove aspects in any combination.

For a better understanding of the invention, and to show how embodimentsof the same may be carried into effect, reference will now be made, byway of example, to the following examples.

EXAMPLES Crosslinking Material Crosslinking Material Example 1

A crosslinking material comprising a homopolymer of maleic acid wasproduced by the following method.

Synthesis of a homopolymer of maleic acid: 240 grams (g) xylene and 240g maleic anhydride were added to a four neck round bottom flask equippedwith a mechanical stir blade, thermocouple and reflux condenser. Themixture was heated to a set point of 60° C. under a nitrogen atmosphere.Once the maleic anhydride was dissolved, 1.2 g of octylamine was addedand the mixture was held for 5 minutes. Next, the mixture was heated to140° C. set point. At 140° C. a solution of 200.4 g xylene and 24 gdi-tertiary butyl peroxide was added over a time period of two hours viaan addition funnel. After the addition was complete, the resin mixturewas then held at 140° C. for two hours. Next, the mixture was cooled to110° C. to prepare the solution for vacuum distillation. At 110° C. thexylene solvent was removed by vacuum distillation to obtain 263.9 g ofdistillate. After 2 hours, the distillation process was stopped and131.4 g of deionized water was added over 60 minutes. After thisaddition, the reactor was set up with a Dean-Stark apparatus to removeresidual xylene. After 1 hour, 306.6 g of deionized water was added over60 min and the reaction was held at 110° C. for 15 min.

Neutralization of a homopolymer of maleic acid with ammonium hydroxide:The resin from the above step was placed in a water bath at roomtemperature and 300 g of ammonium hydroxide (28% solution in water) wasadded over 60 min. After this addition, the mixture was held for 15 minthen poured out into a suitable container.

The resultant crosslinking material had a solids content of 39.9% asmeasured by 110° C. solids test.

Crosslinking Material Example 2

Neutralization of a homopolymer of maleic acid withdimethylethanolamine: A homopolymer of maleic acid was prepared asdescribed in Example 1 starting with 520 g of maleic anhydride. The restof the components were scaled appropriately by a factor of 2.167. Theresin as prepared was heated to a set point of 70° C. Next, 468 g ofdimethylethanolamine was added over 60 min. After this addition, themixture was held for 15 min then poured out into a suitable container.

The resultant crosslinking material had a solids content of 64.5% asmeasured by 110° C. solids test.

Crosslinking Material Example 3

A crosslinking material comprising a copolymer of maleic acid andstyrene was produced by the following method.

160 g xylene and 144 g maleic anhydride were added to a four neck roundbottom flask equipped with a mechanical stir blade, thermocouple andreflux condenser. The mixture was heated to a set point of 60° C. undera nitrogen atmosphere. Once the maleic anhydride was dissolved, themixture was heated to 140° C. set point. At 140° C., a solution of 64 gxylene and 32 g tert-butyl peroxyacetate (50 w/w % solution in aliphatichydrocarbon solvent) was added over a time period of 125 minutes via anaddition funnel. After 5 minutes, a solution of 64 g xylene and 16 gstyrene was added over a time period of 120 minutes via an additionfunnel. After the addition was complete, the resin mixture was then heldat 140° C. for two hours. Next, the mixture was cooled to 110° C. toprepare the solution for vacuum distillation. At 110° C., the xylenesolvent was removed by vacuum distillation to obtain 195.2 g ofdistillate. After 40 minutes, the distillation process was stopped and88 g of deionized water was added over 60 minutes. After this addition,the reactor was set up with a Dean-Stark apparatus to remove residualxylene. After 100 minutes, 204 g of deionized water was added over 30min and the reaction was held at 110° C. for 15 min. The resin wascooled to a set point of 70° C. Next, 144 g of dimethylethanolamine wasadded over 60 min. After this addition, the mixture was held for 15 minthen poured out into a suitable container.

The resultant crosslinking material had a solids content of 55.2% asmeasured by 110° C. solids test.

Crosslinking Material Example 4

A crosslinking material comprising a copolymer of maleic acid andstyrene was produced by the following method.

160 g xylene and 128 g maleic anhydride were added to a four neck roundbottom flask equipped with a mechanical stir blade, thermocouple andreflux condenser. The mixture was heated to a set point of 60° C. undera nitrogen atmosphere. Once the maleic anhydride was dissolved, themixture was heated to 140° C. set point. At 140° C. a solution of 64 gxylene and 32 g tert-butyl peroxyacetate (50 w/w % solution in aliphatichydrocarbon solvent) was added over a time period of 125 minutes via anaddition funnel. After 5 minutes, a solution of 64 g xylene and 32 gstyrene was added over a time period of 120 minutes via an additionfunnel. After the addition was complete, the resin mixture was then heldat 140° C. for two hours. Next, the mixture was cooled to 110° C. toprepare the solution for vacuum distillation. At 110° C. the xylenesolvent was removed by vacuum distillation to obtain 202.2 g ofdistillate. After 40 minutes the distillation process was stopped and 88g of deionized water was added over 60 minutes. After this addition, thereactor was set up with a Dean-Stark apparatus to remove residualxylene. After 60 minutes, 204 g of deionized water was added over 30 minand the reaction was held at 110° C. for 15 min. The resin was cooled toa set point of 70° C. Next, 144 g of dimethylethanolamine was added over60 min. After this addition, the mixture was held for 15 min then pouredout into a suitable container.

The resultant crosslinking material had a solids content of 50.2% asmeasured by 110° C. solids test.

Film-Forming Resin Film-Forming Resin 1

A core shell latex comprising 70 wt % of a core made from 42.5 wt %ethyl acrylate, 50 wt % styrene and 7.5 wt % glycidyl methacrylate and30 wt % of a shell made from 32 wt % ethyl acrylate, 30 wt % styrene and38 wt % acrylic acid was synthesized by known methods using ethyleneglycol monobutyl ether, amyl alcohol and propylene glycol monomethylether as solvents and hydrogen peroxide and benzoin as the initiatorpackage. The final latex was made to 25% solids (based on the totalweight) in deionized water.

Film-Forming Resin 2

760 g glacial Methacrylic Acid, 440 g Butyl Acrylate, 800 g HydroxyethylMethacrylate, 40 g t-butyl peroxy-3,5,5-trimethylhexanoate and 240 gbutyl CELLOSOLVE™ were premixed in a conical flask. A 12-liter flask wasequipped with a motor driven stainless steel stir blade, a water-cooledcondenser, a nitrogen inlet, and a heating mantle with a thermometerconnected through a temperature feedback control device. Added to the12-liter flask was 484.51 g 1-pentanol and 1103.5 g butyl CELLOSOLVE™.The flask was then heated to 138° C. At 138° C., the premix was addedover two and a half hours. 25 g butyl CELLOSOLVE™ was added as rinse. Asecond premix containing 24.61 g t-butyl peroxy-3,5,5-Trimethylhexanoateand 75 g butyl CELLOSOLVE™ was added in two halves, 30 minutes holdafter the first half and one and a half hour hold after the second halfaddition. After the hold, the flask temperature reduced to <100° C. andneutralized with 470.07 g dimethylethanolamine, followed by 3537.60 gdeionized water over 10 minutes. The batch was held for 10 minutes, heatdiscontinued and the batch cooled for analysis and formulation.

Coating Compositions Examples 1-6

Coating examples 1-6 were prepared according to the formulations inTable 1. All amounts are given in grams (g) unless specified otherwise.

TABLE 1 Formulation of Coating Examples 1-6 Example Example ExampleExample Example Example Component 1 2 3 4 5 6 Film-forming 105.6 58.852.80 — — — resin 1 Film-forming — — — 79.6 38.45 38.41 resin 2Crosslinking 10.16 — — — — — material 1 Crosslinking — — — 7.63 — —material 2 Crosslinking — 3.32 — — 4.38 — material 3 Crosslinking — —3.71 — — 4.82 material 4 Deionised 24.28 13.42 12.34 40.05 26.31 25.67water Solvent blend 9.34 4.64 5.56 — — — (butanol/butyl Cellosolve/ amylalcohol 2.6:1:1.03) Solvent blend — — — 10.65 5.24 5.39 (butylCellosolve/ amyl alcohol 2.5:1) Dimethyl- — 0.5 0.52 3.01 1.09 1.45ethanolamine Total 149.38 80.68 74.93 140.94 75.47 75.74 % Solids 20.2220.49 20.10 21.38 19.91 19.83

Comparative Coating Examples 1 and 2

Comparative coating examples 1 and 2 were prepared according to theformulations in Table 2. All amounts are given in grams (g) unlessspecified otherwise.

TABLE 2 Formulation of Comparative Coating Examples 1 and 2 ComparativeComparative Component Example 1 Example 2 Latex acrylic example 1 400.0369.7 Curaphen 40-804 W75 ¹ — 10.2 Deionised water 50.0 50.0 Butanol25.5 25.5 Ethylene glycol n-butyl ether 9.7 9.7 Amyl alcohol 10.0 10.0Dimethylethanolamine 2.0 5.0 Total 497.2 480.2 ¹ phenolic resole resinin deionised water at 74% weight solids, available from BUTREZ Ltd.

The properties of the coatings were the tested according to thefollowing methods. The results are shown in Table 3.

Test Methods

Test panel preparation: the coatings were drawn down onto flat aluminiumcans using either a #14 or a #16 wire bar in order to achieve targetfilm weights in the 5 to 6 g/m² range. The coatings were baked in a boxoven set at 215° C. for one minute and forty-five seconds (1 min 45 s).The dry film weights were determined using a SENCON S19600 CoatingThickness Gauge.

Corrosion resistance: a first set of coated substrates were exposed toboiling (100° C.) 5% acetic acid for 30 minutes in an 800 mL beaker on atemperature-controlled CORNING PC-420D hot plate. A second set of coatedsubstrates were exposed to boiling (100° C.) 3% acetic acid for 30minutes in an 800 mL beaker on a temperature-controlled CORNING PC-420Dhot plate. A third set of coated substrates were exposed to boiling 3%acetic acid for 30 minutes in an 800 mL beaker on atemperature-controlled CORNING PC-420D hot plate followed by storage forten days in 3% acetic acid in a sealed container at 40° C. A fourth setof coated substrates were exposed to a 1% Joy® detergent solution for 10minutes at 82° C. on a temperature-controlled CORNING PC-420D hot plate.The coated substrates were then tested for blistering and adhesion asfollows.

Blistering: blistering was determined according to ASTM D714 (“StandardTest Method for Evaluating Degree of Blistering of Paints”), whichcontains photographic reference standards for the degree of blistering.

Adhesion: The panels were tested for coating adhesion to the substrateusing the BYK Cross-Cut Tester Kit #5127 with a 1.5 mm blade accordingto the manufacturer's instructions. The results were assessed visuallyand rated from 0 to 5, with 0 meaning no loss of adhesion, 1 meaning <5%loss of adhesion, 2 meaning a 5% to 15% loss of adhesion, 3 meaning a16% to 35% loss of adhesion, 4 meaning a 36% to 65% loss of adhesion and5 meaning an >65% loss of adhesion. The loss percentage was assessed inthe area of the scribe.

MEK double rubs: MEK resistance was determined using a two pound ballhammer using MEK soaked gauze covering the ball end of the hammer. Thenumber of double rubs until the coating failed to the substrate wasrecorded.

Flexibility: the coating compositions were drawn down on tinplatesubstrate for flexibility testing using an BYK Gardner Impact Tester toapply a 48 inch-lbs impact force to the coated and folded tinplatepanels. The coated panels were then rusted by exposure to a solution of15% copper sulphate and 7.5% hydrochloric acid in deionised water fortwo minutes. After this time, the amount of rust-free length wasrecorded (the total tinplate length being 100 mm). The length inmillimetres (mm) of the coated panel that is free from continuousrusting and spotted or peppering rusting was recorded.

Test Results

TABLE 3 Results for Coating Examples 1-6 and Comparative CoatingExamples 1 and 2 Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 1Ex. 2 Dry film 5.7 4.9 4.6 4.8 4.5 4.2 5.8 5.7 weight (g/m²) MEK double6 12 16 100+ 100+ 100+ 10 27 rubs Flexibility 84 66 70 42 44 25 66 54(continuous) Flexibility 79 51 45 26 29 21 78 68 (peppering) Corrosionresistance—1% Joy (RTM) Detergent, 82° C. for 10 mins Adhesion — — — — —0 0 Blistering — — — — — OK OK Corrosion resistance—1% Joy (RTM)Detergent, 82° C. for 45 mins Adhesion 0 0 0 0 0 0 — — Blistering OK OKOK OK OK OK — — Corrosion resistance—3% acetic acid, 100° C. for 30 minsAdhesion — — — — — — 0 0 Blistering — — — — — — Light OK blush Corrosionresistance—3% acetic acid, 100° C. for 30 mins + 10 day storage at 40°C. Adhesion 0 1 1 0 1 1 2 2 Blistering OK #8 few #8 few Matte, #8 #8Matte, Dense micro- medium, medium, large #8 blisters micro- micro-blisters + blisters blisters blisters dense #8 blisters Corrosionresistance—5% acetic acid, 100° C. for 30 mins Adhesion 0 0 0 0 1 1 3 3Blistering OK OK OK Few Micro- Micro- Dense Medium micro- blistersblisters #2 dense blisters blisters + #2 blush blisters + blush

The results show that the coating compositions according to the presentinvention perform as well, or better, than the coatings of thecomparative examples.

Attention is directed to all papers and documents which are filedconcurrently with or previous to this specification in connection withthis application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1-52. (canceled)
 53. A crosslinking material, the crosslinking materialcomprising the reaction product of a reaction mixture comprising: (i)≥70% by weight of a cyclic unsaturated acid anhydride and/or diacidderivative thereof by total solid weight of the monomers from which thecrosslinking material is formed; (ii) optionally, an ethylenicallyunsaturated monomer; and (iii) optionally, an alcohol, amine, thioland/or water, wherein at least a portion of the cyclic unsaturated acidanhydride and/or diacid derivative thereof is reacted with the alcohol,amine, thiol and/or water, when present; and wherein the crosslinkingmaterial has an acid number of at least 100 mg KOH/g.
 54. Thecrosslinking material according to claim 53, wherein the cyclicunsaturated acid anhydride comprises maleic anhydride.
 55. Thecrosslinking material according to claim 53, wherein the reactionmixture comprises an ethylenically unsaturated monomer (ii) and whereinthe ethylenically unsaturated monomer comprises a hydroxyl functionalmonomer.
 56. The crosslinking material according to claim 55, whereinthe crosslinking material comprises ≥2.5% hydroxyl functionalethylenically unsaturated monomer based on the total solid weight of themonomers from which the crosslinking material is formed.
 57. Thecrosslinking material according to claim 53, wherein the crosslinkingmaterial comprises an ethylenically unsaturated monomer, and wherein theethylenically unsaturated monomer comprises styrene, a vinyl ethermonomer, vinyl acetate or combinations thereof.
 58. The crosslinkingmaterial according to claim 55, wherein the unsaturated acid anhydrideand/or diacid derivative thereof comprises maleic anhydride and theethylenically unsaturated monomer(s) comprises a hydroxyl functionalmonomer with styrene, isobutyl vinyl ether and/or vinyl acetate.
 59. Thecrosslinking material according to claim 53, wherein the crosslinkingmaterial has a Tg of at least 50° C.
 60. The crosslinking materialaccording to claim 53, wherein the reaction mixture comprises analcohol, amine, thiol and/or water (iii), wherein at least a portion ofthe cyclic unsaturated acid anhydride and/or diacid derivative thereofis reacted with the alcohol, amine, thiol and/or water.
 61. Thecrosslinking material according to claim 60, wherein the amine and/orthiol is hydroxy functional.
 62. The crosslinking material according toclaim 60, wherein the crosslinking material comprises the reactionproduct of a reaction mixture wherein ≥10% of the cyclic unsaturatedacid anhydride and/or diacid derivative thereof is reacted with an amineand/or thiol comprising one or more hydroxy groups, and/or an alcoholcomprising two or more hydroxy groups.
 63. The crosslinking materialaccording to claim 53, wherein the crosslinking material comprises atleast 75 wt % of cyclic unsaturated acid anhydride and/or diacidderivative thereof based on the total solid weight of the monomers fromwhich the crosslinking material is formed.
 64. The crosslinking materialaccording to claim 53, wherein the crosslinking material has an acidnumber of at least 200 mg KOH/g.
 65. The crosslinking material accordingto claim 53, wherein the crosslinking material has a hydroxyl number of≥2 mg KOH/g.
 66. The crosslinking material according to claim 53,wherein crosslinking material has an Mn of at least 300 Da.
 67. Thecrosslinking material according to claim 53, wherein the crosslinkingmaterial is substantially free of formaldehyde.
 68. A coatingcomposition, the coating composition comprising: (a) a film-formingresin having a functional group having an active hydrogen atom; and (b)a crosslinking material comprising the reaction product of a reactionmixture comprising: (i) ≥70% by weight of a cyclic unsaturated acidanhydride and/or diacid derivative thereof by total solid weight of themonomers from which the crosslinking material is formed; (ii)optionally, an ethylenically unsaturated monomer; and (iii) optionally,an alcohol, amine, thiol and/or water, wherein at least a portion of thecyclic unsaturated acid anhydride and/or diacid derivative thereof isreacted with the alcohol, amine, thiol and/or water, when present; andwherein the crosslinking material has an acid number of at least 100 mgKOH/g.
 69. The coating composition according to claim 68, wherein thefilm-forming resin comprises an acrylic material.
 70. The coatingcomposition according to claim 69, wherein the acrylic material isformed from ≥10% hydroxyl functional acrylic monomer by total solidweight of the monomers from which the acrylic material is formed. 71.The coating composition according to claim 69, wherein the acrylicmaterial is formed from ≥20% (meth)acrylic acid by total solid weight ofthe monomers from which the acrylic material is formed.
 72. A substratecoated on at least a portion thereof with a coating, the coating beingderived from a coating composition comprising (a) a film-forming resinhaving a functional group having an active hydrogen atom; and (b) acrosslinking material comprising the reaction product of a reactionmixture comprising: (i) ≥70% by weight of a cyclic unsaturated acidanhydride and/or diacid derivative thereof by total solid weight of themonomers from which the crosslinking material is formed; (ii)optionally, an ethylenically unsaturated monomer; and (iii) optionally,an alcohol, amine, thiol and/or water, wherein at least a portion of thecyclic unsaturated acid anhydride and/or diacid derivative thereof isreacted with the alcohol, amine, thiol and/or water, when present; andwherein the crosslinking material has an acid number of at least 100 mgKOH/g.
 73. A package coated on at least a portion thereof with acoating, the coating being derived from a coating composition comprising(a) a film-forming resin having a functional group having an activehydrogen atom; and (b) a crosslinking material comprising the reactionproduct of a reaction mixture comprising: (i) ≥70% by weight of a cyclicunsaturated acid anhydride and/or diacid derivative thereof by totalsolid weight of the monomers from which the crosslinking material isformed; (ii) optionally, an ethylenically unsaturated monomer; and (iii)optionally, an alcohol, amine, thiol and/or water, wherein at least aportion of the cyclic unsaturated acid anhydride and/or diacidderivative thereof is reacted with the alcohol, amine, thiol and/orwater, when present; and wherein the crosslinking material has an acidnumber of at least 100 mg KOH/g.
 74. The package according to claim 73,wherein the package is a metal food and/or beverage can, and/or amonobloc aerosol can and/or tube.